Exhibit 99.1

[FORM OF PRELIMINARY PROSPECTUS SUPPLEMENT TO BE USED IN

CONJUNCTION WITH FUTURE COMMON STOCK OFFERINGS](1)

PRELIMINARY PROSPECTUS SUPPLEMENT

(to Prospectus dated , 20 )

[ ] Shares

New Mountain Finance Corporation

Common Stock

New Mountain Finance Corporation (“NMFC”, the “Company”, “we”, “us” and “our”) is a Delaware corporation that was originally incorporated on June 29, 2010. We are a closed-end, non-diversified management investment company that has elected to be regulated as a business development company under the Investment Company Act of 1940, as amended. Our investment objective is to generate current income and capital appreciation through the sourcing and origination of debt securities at all levels of the capital structure, including first and second lien debt, notes, bonds and mezzanine securities. Our first lien debt may include traditional first lien senior secured loans or unitranche loans. Unitranche loans combine characteristics of traditional first lien senior secured loans as well as second lien and subordinated loans. Unitranche loans will expose us to the risks associated with second lien and subordinated loans to the extent we invest in the “last out” tranche. In some cases, our investments may also include equity interests. Our primary focus is in the debt of defensive growth companies, which are defined as generally exhibiting the following characteristics: (i) sustainable secular growth drivers, (ii) high barriers to competitive entry, (iii) high free cash flow after capital expenditure and working capital needs, (iv) high returns on assets and (v) niche market dominance.

The investments that we invest in are almost entirely rated below investment grade or may be unrated, which are often referred to as “leveraged loans”, “high yield” or “junk” debt investments, and may be considered “high risk” or speculative compared to debt investments that are rated investment grade. Such issuers are considered more likely than investment grade issuers to default on their payments of interest and principal and such risk of default could reduce our net asset value and income distributions. Our investments are also primarily floating rate debt investments that contain interest reset provisions that may make it more difficult for borrowers to make debt repayments to us if interest rates rise. In addition, some of our debt investments will not fully amortize during their lifetime, which could result in a loss or a substantial amount of unpaid principal and interest due upon maturity. Our debt investments may also lose significant market value before a default occurs. Furthermore, an active trading market may not exist for these securities. This illiquidity may make it more difficult to value our investments.

We are offering for sale shares of NMFC’s common stock. We have granted the underwriters a [ ]-day option to purchase up to additional shares of NMFC’s common stock at the public offering price, less the underwriting discounts and commissions.

Our common stock is traded on the New York Stock Exchange under the symbol “NMFC”. On [ ], the last reported sales price on the New York Stock Exchange for our common stock was $[ ] per share.

(1) In addition to the sections outlined in this form of prospectus supplement, each prospectus supplement actually used in connection with an offering conducted pursuant to the registration statement to which this form of prospectus supplement is attached will be updated to include such other information as may then be required to be disclosed therein pursuant to applicable law or regulation as in effect as of the date of each such prospectus supplement, including, without limitation, information particular to the terms of each security offered thereby and any related risk factors or tax considerations pertaining thereto. This form of prospectus supplement is intended only to provide a rough approximation of the nature and type of disclosure that may appear in any actual prospectus supplement used for the purposes of offering securities pursuant to the registration statement to which this form of prospectus supplement is attached, and is not intended to and does not contain all of the information that would appear is any such actual prospectus supplement, and should not be used or relied upon in connection with any offer or sale of securities.

An investment in NMFC’s common stock is very risky and highly speculative. Shares of closed-end investment companies, including business development companies, frequently trade at a discount to their net asset value. In addition, the companies in which NMFC invests are subject to special risks. See “Risk Factors” beginning on page [ ] of the accompanying prospectus to read about factors you should consider, including the risk of leverage, before investing in NMFC’s common stock.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

This prospectus supplement and the accompanying prospectus contain important information about NMFC that a prospective investor should know before investing in NMFC’s common stock. Please read this prospectus supplement and the accompanying prospectus before investing and keep it for future reference. NMFC files annual, quarterly and current reports, proxy statements and other information with the Securities and Exchange Commission (http://www.sec.gov), which is available free of charge by contacting NMFC by mail at 787 Seventh Avenue, 48th Floor, New York, New York 10019 or on our website at http://www.newmountainfinance.com. Information contained on our website is not incorporated by reference into this prospectus supplement and the accompanying prospectus, and you should not consider that information to be part of this prospectus supplement and the accompanying prospectus.

	Per Share	Total
Public Offering Price	$	$
Sales Load (Underwriting Discounts and Commissions)	$	$
Proceeds to us (before expenses)	$	$

(1) All expenses of the offering, including the sales load, will be borne by NMFC. NMFC will incur approximately $[ ] of estimated expenses, excluding the sales load, in connection with this offering. Stockholders will indirectly bear such expenses, including the sales load.

(2) To the extent that the underwriters sell more than [ ] shares of NMFC’s common stock, the underwriters have the option to purchase up to an additional [ ] shares of NMFC’s common stock at the public offering price, less the sales load, within [ ] days of the date of this prospectus. If the underwriters exercise this option in full, the total public offering price, sales load and proceeds to us will be $ , $ and $ , respectively.

The underwriters expect to deliver the shares against payment in New York, New York on or about , 20 .

, 20

TABLE OF CONTENTS

PROSPECTUS SUPPLEMENT

	Page

ABOUT THIS PROSPECTUS SUPPLEMENT	S-ii

PROSPECTUS SUPPLEMENT SUMMARY	S-1

OFFERING	S-9

FEES AND EXPENSES	S-12

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS	S-14

CAPITALIZATION	S-16

USE OF PROCEEDS	S-16

UNDERWRITING	S-19

LEGAL MATTERS	S-21

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM	S-21

AVAILABLE INFORMATION	S-22

PROSPECTUS

[Insert table of contents from the base prospectus]

S-i

ABOUT THIS PROSPECTUS SUPPLEMENT

You should rely only on the information contained in this prospectus supplement and the accompanying prospectus. Neither we nor the underwriters have authorized any other person to provide you with different information from that contained in this prospectus supplement or the accompanying prospectus. If anyone provides you with different or inconsistent information, you should not rely on it. This prospectus supplement and the accompanying prospectus do not constitute an offer to sell, or a solicitation of an offer to buy, any shares of our common stock by any person in any jurisdiction where it is unlawful for that person to make such an offer or solicitation or to any person in any jurisdiction to whom it is unlawful to make such an offer or solicitation. The information contained in this prospectus supplement and the accompanying prospectus is complete and accurate only as of their respective dates, regardless of the time of their delivery or sale of our common stock. This prospectus supplement supersedes the accompanying prospectus to the extent it contains information different from or additional to the information in that prospectus.

This document is in two parts. The first part is this prospectus supplement, which describes the terms of this offering of common stock and also adds to and updates information contained in the accompanying prospectus. The second part is the accompanying prospectus, which gives more general information and disclosure. To the extent the information contained in this prospectus supplement differs from the information contained in the accompanying prospectus, the information in this prospectus supplement shall control. Please carefully read this prospectus supplement and the accompanying prospectus together with any exhibits and the additional information described under “Available Information” and in the “Summary” and “Risk Factors” sections before you make an investment decision.

S-ii

PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights some of the information in this prospectus supplement and the accompanying prospectus. It is not complete and may not contain all of the information that you may want to consider. You should read carefully the more detailed information set forth under “Risk Factors” and the other information included in this prospectus supplement and the accompanying prospectus and the documents to which we have referred.

In this prospectus supplement, unless the context otherwise requires, references to:

· “NMFC”, the “Company”, “we”, “us” and “our” refers to New Mountain Finance Corporation, a Delaware corporation, which was incorporated on June 29, 2010, including, where appropriate, its wholly-owned direct and indirect subsidiaries;

· “NMF Holdings” and “Predecessor Operating Company” refers to New Mountain Finance Holdings, L.L.C., a Delaware limited liability company;

· “NMF SLF” refers to New Mountain Finance SPV Funding, L.L.C., a Delaware limited liability company;

· “SBIC GP” refers to New Mountain Finance SBIC G.P. L.L.C., a Delaware limited liability company;

· “SBIC LP” refers to New Mountain Finance SBIC L.P., a Delaware limited partnership;

· “Guardian AIV” refers to New Mountain Guardian AIV, L.P.;

· “AIV Holdings” refers to New Mountain Finance AIV Holdings Corporation, a Delaware corporation which was incorporated on March 11, 2011, of which Guardian AIV was the sole stockholder;

· “Investment Adviser” refers to New Mountain Finance Advisers BDC, L.L.C., our investment adviser;

· “Administrator” refers to New Mountain Finance Administration, L.L.C., our administrator;

· “New Mountain Capital” refers to New Mountain Capital Group, L.L.C. and its affiliates;

· “Predecessor Entities” refers to New Mountain Guardian (Leveraged), L.L.C. and New Mountain Guardian Partners, L.P., together with their respective direct and indirect wholly-owned subsidiaries prior to our initial public offering;

· “NMFC Credit Facility” refers to our Senior Secured Revolving Credit Agreement with Goldman Sachs Bank USA, Morgan Stanley Bank, N.A. and Stifel Bank & Trust, dated June 4, 2014, as amended (together with the related guarantee and security agreement);

· “Holdings Credit Facility” refers to NMF Holdings’ Second Amended and Restated Loan and Security Agreement with Wells Fargo Bank, National Association, dated December 18, 2014;

· “Predecessor Holdings Credit Facility” refers to NMF Holdings’ Amended and Restated Loan and Security Agreement with Wells Fargo Bank, National Association, dated May 19, 2011, as amended

· “SLF Credit Facility” refers to NMF SLF’s Loan and Security Agreement with Wells Fargo Bank, National Association, dated October 27, 2010, as amended;

· “Convertible Notes” refers to our 5.00% convertible notes due 2019 issued on June 3, 2014 and September 30, 2016 under an indenture dated June 3, 2014 (the “Indenture”), between us and U.S. Bank National Association, as trustee; and

S-1

· “Unsecured Notes” refers to our 5.313% unsecured notes due May 15, 2021 issued on May 6, 2016 and September 30, 2016, to institutional investors in a private placement.

For the periods prior to and as of December 31, 2013, all financial information provided in this prospectus supplement reflects our organizational structure prior to the restructuring on May 8, 2014 described under “Description of Restructuring” in the accompanying prospectus, where NMF Holdings functioned as the operating company.

Overview

We are a Delaware corporation that was originally incorporated on June 29, 2010 and completed our initial public offering (“IPO”) on May 19, 2011. We are a closed-end, non-diversified management investment company that has elected to be regulated as a business development company (“BDC”) under the Investment Company Act of 1940, as amended (the “1940 Act”). As such, we are obligated to comply with certain regulatory requirements. We have elected to be treated, and intend to comply with the requirements to continue to qualify annually, as a regulated investment company (“RIC”) under Subchapter M of the Internal Revenue Code of 1986, as amended, (the “Code”). We are also registered as an investment adviser under the Investment Advisers Act of 1940, as amended (the “Advisers Act”).

The Investment Adviser is a wholly-owned subsidiary of New Mountain Capital. New Mountain Capital is a firm with a track record of investing in the middle market and with assets under management of approximately $[ ](1), which includes total assets held by us. New Mountain Capital focuses on investing in defensive growth companies across its private equity, public equity and credit investment vehicles. The Investment Adviser manages our day-to-day operations and provides us with investment advisory and management services. The Administrator, a wholly-owned subsidiary of New Mountain Capital, provides the administrative services necessary to conduct our day-to-day operations.

Our wholly-owned subsidiary, NMF Holdings, is a Delaware limited liability company whose assets are used to secure NMF Holdings’ credit facility. For additional information about our organizational structure prior to May 8, 2014, see “Description of Restructuring” in the accompanying prospectus. NMF Ancora Holdings Inc. (“NMF Ancora”), NMF QID NGL Holdings, Inc. (“NMF QID”) and NMF YP Holdings Inc. (“NMF YP”), our wholly-owned subsidiaries, are structured as Delaware entities that serve as tax blocker corporations which hold equity or equity-like investments in portfolio companies organized as limited liability companies (or other forms of pass-through entities). We consolidate our tax blocker corporations for accounting purposes. The tax blocker corporations are not consolidated for income tax purposes and may incur income tax expense as a result of their ownership of the portfolio companies. Additionally, our wholly-owned subsidiary, New Mountain Finance Servicing, L.L.C. (“NMF Servicing”), serves as the administrative agent on certain investment transactions. SBIC LP, and its general partner, SBIC GP, were organized in Delaware as a limited partnership and limited liability company, respectively. SBIC LP and SBIC GP are our consolidated wholly-owned direct and indirect subsidiaries. SBIC LP received a license from the United States (“U.S.”) Small Business Administration (the “SBA”) to operate as a small business investment company (“SBIC”) under Section 301(c) of the Small Business Investment Act of 1958, as amended (the “1958 Act”). Our wholly-owned subsidiary, NMNLC, a Maryland corporation, was formed to acquire commercial real properties that are subject to “triple net” leases and intends to qualify as a real estate investment trust, or REIT, within the meaning of Section 856(a) of the Code.

(1) Includes amounts committed, not all of which have been drawn down and invested to-date, as of [ ], as well as amounts called and returned since inception.

S-2

Our investment objective is to generate current income and capital appreciation through the sourcing and origination of debt securities at all levels of the capital structure, including first and second lien debt, notes, bonds and mezzanine securities. Our first lien debt may include traditional first lien senior secured loans or unitranche loans. Unitranche loans combine characteristics of traditional first lien senior secured loans as well as second lien and subordinated loans. Unitranche loans will expose us to the risks associated with second lien and subordinated loans to the extent we invest in the “last out” tranche. In some cases, our investments may also include equity interests. The primary focus is in the debt of defensive growth companies, which are defined as generally exhibiting the following characteristics: (i) sustainable secular growth drivers, (ii) high barriers to competitive entry, (iii) high free cash flow after capital expenditure and working capital needs, (iv) high returns on assets and (v) niche market dominance. Similar to us, SBIC LP’s investment objective is to generate current income and capital appreciation under our investment criteria. However, SBIC LP’s investments must be in SBA eligible companies. Our portfolio may be concentrated in a limited number of industries.

As of [ ], our net asset value was $[ ] million and our portfolio had a fair value of approximately $[ ] million in [ ] portfolio companies, with a weighted average yield to maturity at cost (“Yield to Maturity at Cost”) of approximately [ ]. This Yield to Maturity at Cost calculation assumes that all investments, including secured collateralized agreements, not on non-accrual are purchased at cost on the quarter end date and held until their respective maturities with no prepayments or losses and exited at par at maturity. Adjusted cost reflects the accounting principles generally accepted in the United States of America (“GAAP”) cost for post-IPO investments and a stepped up cost basis of pre-IPO investments (assuming a step-up to fair market value occurred on the IPO date). This calculation excludes the impact of existing leverage. Yield to Maturity at Cost uses the London Interbank Offered Rate (“LIBOR”) curves at each quarter’s end date. The actual yield to maturity may be higher or lower due to the future selection of the LIBOR contracts by the individual companies in our portfolio or other factors.

Recent Developments

[Insert Recent Developments at the Time of the Offering]

The Investment Adviser

The Investment Adviser, a wholly-owned subsidiary of New Mountain Capital, manages our day-to-day operations and provides us with investment advisory and management services. In particular, the Investment Adviser is responsible for identifying attractive investment opportunities, conducting research and due diligence on prospective investments, structuring our investments and monitoring and servicing our investments. We currently do not have, and do not intend to have, any employees. The Investment Adviser also manages New Mountain Guardian Partners II, L.P., a Delaware limited partnership, and New Mountain Guardian Partners II Offshore, L.P., a Cayman Islands exempted limited partnership, (together “Guardian II”), which commenced operations in April 2017. As of [ ], the Investment Adviser was supported by approximately [ ] staff members of New Mountain Capital, including approximately [ ] investment professionals.

The Investment Adviser is managed by a five member investment committee (the “Investment Committee”), which is responsible for approving purchases and sales of our investments above $10.0 million in aggregate by

S-3

issuer. The Investment Committee currently consists of Steven B. Klinsky, Robert A. Hamwee, Adam B. Weinstein and John R. Kline. The fifth and final member of the Investment Committee will consist of a New Mountain Capital Managing Director who will hold the position on the Investment Committee on an annual rotating basis. Beginning in August 2016, Mathew J. Lori was appointed to the Investment Committee for a one year term. In addition, our executive officers and certain investment professionals of the Investment Adviser are invited to all Investment Committee meetings. Purchases and dispositions below $10.0 million may be approved by our Chief Executive Officer. These approval thresholds are subject to change over time. We expect to benefit from the extensive and varied relevant experience of the investment professionals serving on the Investment Committee, which includes expertise in private equity, primary and secondary leveraged credit, private mezzanine finance and distressed debt.

Competitive Advantages

We believe that we have the following competitive advantages over other capital providers to middle market companies:

Proven and Differentiated Investment Style With Areas of Deep Industry Knowledge

In making its investment decisions, the Investment Adviser applies New Mountain Capital’s long-standing, consistent investment approach that has been in place since its founding more than 15 years ago. We focus on companies in defensive growth niches of the middle market space where we believe few debt funds have built equivalent research and operational size and scale.

We benefit directly from New Mountain Capital’s private equity investment strategy that seeks to identify attractive investment sectors from the top down and then works to become a well positioned investor in these sectors. New Mountain Capital focuses on companies and industries with sustainable strengths in all economic cycles, particularly ones that are defensive in nature, that have secular tailwinds and can maintain pricing power in the midst of a recessionary and/or inflationary environment. New Mountain Capital focuses on companies within sectors in which it has significant expertise (examples include software, education, niche healthcare, business services, federal services and distribution & logistics) while typically avoiding investments in companies with products or services that serve markets that are highly cyclical, have the potential for long-term decline, are overly-dependent on consumer demand or are commodity-like in nature.

In making its investment decisions, the Investment Adviser has adopted the approach of New Mountain Capital, which is based on three primary investment principles:

1. A generalist approach, combined with proactive pursuit of the highest quality opportunities within carefully selected industries, identified via an intensive and structured ongoing research process;

2. Emphasis on strong downside protection and strict risk controls; and

3. Continued search for superior risk adjusted returns, combined with timely, intelligent exits and outstanding return performance.

S-4

Experienced Management Team and Established Platform

The Investment Adviser’s team members have extensive experience in the leveraged lending space. Steven B. Klinsky, New Mountain Capital’s Founder, Chief Executive Officer and Managing Director and Chairman of our board of directors, was a general partner of Forstmann Little & Co., a manager of debt and equity funds totaling multiple billions of dollars in the 1980s and 1990s. He was also a co-founder of Goldman, Sachs & Co.’s Leverage Buyout Group in the period from 1981 to 1984. Robert A. Hamwee, our Chief Executive Officer and Managing Director of New Mountain Capital, was formerly President of GSC Group, Inc. (“GSC”), where he was the portfolio manager of GSC’s distressed debt funds and led the development of GSC’s CLOs. John R. Kline, our President and Chief Operating Officer and Managing Director of New Mountain Capital, worked at GSC as an investment analyst and trader for GSC’s control distressed and corporate credit funds and at Goldman, Sachs & Co. in the Credit Risk Management and Advisory Group.

Many of the debt investments that we have made to date have been in the same companies with which New Mountain Capital has already conducted months of intensive acquisition due diligence related to potential private equity investments. We believe that private equity underwriting due diligence is usually more robust than typical due diligence for loan underwriting. In its underwriting of debt investments, the Investment Adviser is able to utilize the research and hands-on operating experience that New Mountain Capital’s private equity underwriting teams possess regarding the individual companies and industries. Business and industry due diligence is led by a team of investment professionals of the Investment Adviser that generally consists of three to seven individuals, typically based on their relevant company and/or industry specific knowledge. Additionally, the Investment Adviser is also able to utilize its relationships with operating management teams and other private equity sponsors. We believe this differentiates us from many of our competitors.

Significant Sourcing Capabilities and Relationships

We believe the Investment Adviser’s ability to source attractive investment opportunities is greatly aided by both New Mountain Capital’s historical and current reviews of private equity opportunities in the business segments we target. To date, a significant majority of the investments that we have made are in the debt of companies and industry sectors that were first identified and reviewed in connection with New Mountain Capital’s private equity efforts, and the majority of our current pipeline reflects this as well. Furthermore, the Investment Adviser’s investment professionals have deep and longstanding relationships in both the private equity sponsor community and the lending/agency community which they have and will continue to utilize to generate investment opportunities.

Risk Management through Various Cycles

New Mountain Capital has emphasized tight control of risk since its inception and long before the recent global financial distress began. To date, New Mountain Capital has never experienced a bankruptcy of any of its portfolio companies in its private equity efforts. The Investment Adviser seeks to emphasize tight control of risk with our investments in several important ways, consistent with New Mountain Capital’s historical approach. In particular, the Investment Adviser:

· Emphasizes the origination or purchase of debt in what the Investment Adviser believes are defensive growth companies, which are less likely to be dependent on macro-economic cycles;

S-5

· Targets investments in companies that are preeminent market leaders in their own industries, and when possible, investments in companies that have strong management teams whose skills are difficult for competitors to acquire or reproduce; and

· Targets investments in companies with significant equity value in excess of our debt investments.

Access to Non Mark to Market, Seasoned Leverage Facility

The amount available under the Holdings Credit Facility is generally not subject to reduction as a result of mark to market fluctuations in our portfolio investments. None of our credit facilities mature prior to June 2019. For a detailed discussion of our credit facilities, see “Management’s Discussion and Analysis of Financial Conditions and Results of Operations — Liquidity and Capital Resources” in the accompanying prospectus.

Market Opportunity

We believe that the size of the market for investments that we target, coupled with the demands of middle market companies for flexible sources of capital at competitive terms and rates, create an attractive investment environment for us.

· Large pool of uninvested private equity capital available for new buyouts. We expect that private equity firms will continue to pursue acquisitions and will seek to leverage their equity investments with mezzanine loans and/or senior loans (including traditional first and second lien, as well as unitranche loans) provided by companies such as ours.

· The leverage finance market has a high level of financing needs over the next several years due to significant bank debt maturities. We believe that the large dollar volume of loans that need to be refinanced will present attractive opportunities to invest capital in a manner consistent with our stated objectives.

· Middle market companies continue to face difficulties in accessing the capital markets. We believe opportunities to serve the middle market will continue to exist. While many middle market companies were formerly able to raise funds by issuing high-yield bonds, we believe this approach to financing has become more difficult as institutional investors have sought to invest in larger, more liquid offerings.

· Increased regulatory scrutiny of banks has reduced middle market lending. We believe that many traditional bank lenders to middle market businesses have either exited or de-emphasized their service and product offerings in the middle market. These traditional lenders have instead focused on lending and providing other services to large corporate clients. We believe this has resulted in fewer key players and the reduced availability of debt capital to the companies we target.

· Conservative loan to value. As a result of the credit crisis, many lenders are requiring larger equity contributions from financial sponsors. Larger equity contributions create an enhanced margin of safety for lenders because leverage is a lower percentage of the implied enterprise value of the company.

· Attractive pricing. Reduced access to, and availability of, debt capital typically increases the interest rates, or pricing, of loans for middle market lenders. Recent primary debt transactions in this market often include upfront fees, original issue discount, prepayment protections and, in some cases, warrants to purchase common stock, all of which should enhance the profitability of new loans to lenders.

S-6

Operating and Regulatory Structure

We are a closed-end, non-diversified management investment company that has elected to be regulated as a BDC under the 1940 Act and are required to maintain an asset coverage ratio, as defined in the 1940 Act, of at least 200.0%. We include the assets and liabilities of our consolidated subsidiaries for purposes of satisfying the requirements under the 1940 Act. See “Regulation — Senior Securities” in the accompanying prospectus..

We have elected to be treated, and intend to comply with the requirements to continue to qualify annually, as a RIC under Subchapter M of the Code. See “Material Federal Income Tax Considerations” in the accompanying prospectus. As a RIC, we generally will not be subject to corporate-level U.S. federal income taxes on any net ordinary income or capital gains that we timely distribute to our stockholders as dividends if it meets certain source-of-income, distribution and asset diversification requirements. We intend to distribute to our stockholders substantially all of our annual taxable income except that we may retain certain net capital gains for reinvestment.

Risks

An investment in our common stock involves risk, including the risk of leverage and the risk that our operating policies and strategies may change without prior notice to our stockholders or prior stockholder approval. See “Risk Factors” and the other information included in this prospectus supplement and the accompanying prospectus for a discussion of factors you should carefully consider before deciding to invest in our common stock. The value of our assets, as well as the market price of our shares, will fluctuate. Our investments may be risky, and you may lose all or part of your investment. Investing in us involves other risks, including the following:

· We may suffer credit losses;

· We do not expect to replicate the Predecessor Entities’ historical performance or the historical performance of other entities managed or supported by New Mountain Capital;

· There is uncertainty as to the value of our portfolio investments because most of our investments are, and may continue to be in private companies and recorded at fair value;

· Our ability to achieve our investment objective depends on key investment personnel of the Investment Adviser. If the Investment Adviser were to lose any of its key investment personnel, our ability to achieve our investment objective could be significantly harmed;

· The Investment Adviser has limited experience managing a BDC or a RIC, which could adversely affect our business;

· We operate in a highly competitive market for investment opportunities and may not be able to compete effectively;

S-7

· Our investments in securities rated below investment grade are speculative in nature and are subject to additional risk factors such as increased possibility of default, illiquidity of the security, and changes in value based on changes in interest rates;

· Our business, results of operations and financial condition depends on our ability to manage future growth effectively;

· We borrow money, which could magnify the potential for gain or loss on amounts invested in us and increase the risk of investing in us;

· Changes in interest rates may affect our cost of capital and net investment income;

· Regulations governing the operations of BDCs will affect our ability to raise additional equity capital as well as our ability to issue senior securities or borrow for investment purposes, any or all of which could have a negative effect on our investment objectives and strategies;

· We may experience fluctuations in our annual and quarterly results due to the nature of our business;

· Our board of directors may change our investment objective, operating policies and strategies without prior notice or stockholder approval, the effects of which may be adverse to your interests;

· We will be subject to corporate-level U.S. federal income tax on all of our income if we are unable to maintain RIC status under Subchapter M of the Code, which would have a material adverse effect on our financial performance;

· We may not be able to pay you distributions on our common stock, our distributions to you may not grow over time and a portion of our distributions to you may be a return of capital for U.S. federal income tax purposes;

· Our investments in portfolio companies may be risky, and we could lose all or part of any of our investments;

· The lack of liquidity in our investments may adversely affect our business;

· Economic recessions, downturns or government spending cuts could impair our portfolio companies and harm our operating results;

· The market price of our common stock may fluctuate significantly; and

· Sales of substantial amounts of our common stock in the public market may have an adverse effect on the market price of our preferred stock.

Company Information

Our administrative and executive offices are located at 787 Seventh Avenue, 48th Floor, New York, New York 10019, and our telephone number is (212) 720-0300. We maintain a website at http://www.newmountainfinance.com. Information contained on our website is not incorporated by reference into

S-8

this prospectus supplement and the accompanying prospectus, and you should not consider information contained on our website to be part of this prospectus supplement and the accompanying prospectus.

Presentation of Historical Financial Information and Market Data

Historical Financial Information

Unless otherwise indicated, historical references contained in the accompanying prospectus for periods prior to and as of December 31, 2013 in “Selected Financial and Other Data”, “Selected Quarterly Data”, “Management’s Discussion and Analysis of Financial Condition and Results of Operations”, “Senior Securities” and “Portfolio Companies” relate to NMF Holdings. The consolidated financial statements of New Mountain Finance Holdings, L.L.C., formerly known as New Mountain Guardian (Leveraged), L.L.C., and New Mountain Guardian Partners, L.P. are NMF Holdings’ historical consolidated financial statements.

Market Data

Statistical and market data used in this prospectus supplement and the accompanying prospectus has been obtained from governmental and independent industry sources and publications. We have not independently verified the data obtained from these sources, and we cannot assure you of the accuracy or completeness of the data. Forward-looking information obtained from these sources is subject to the same qualifications and the additional uncertainties regarding the other forward-looking statements contained in this prospectus supplement and the accompanying prospectus. See “Cautionary Statement Regarding Forward-Looking Statements”.

THE OFFERING

Common Stock Offered by NMFC		shares, excluding shares of common stock issuable pursuant to the option to purchase additional shares granted to the underwriters.

Common Stock Outstanding Prior to This Offering		shares.

Common Stock Outstanding After This Offering		shares, excluding shares of common stock issuable pursuant to the option to purchase additional shares granted to the underwriters.

Use of Proceeds		We intend to use the net proceeds from the sale of our common stock for new investments in portfolio companies in accordance with our investment objective and strategies described in this prospectus supplement and the accompanying prospectus, to temporarily repay indebtedness (which will be subject to reborrowing), to pay our operating expenses and distributions to our stockholders/unit holders and for general corporate purposes. Pending such use, We will invest the net proceeds primarily in cash, cash equivalents, U.S. government securities and other high-quality investments that mature in one year or less from the date of the investment. These securities may have lower yields than the types of investments we would typically make in accordance with our investment objective and, accordingly, may result in lower distributions, if any, during such period. See “Use of Proceeds” in this prospectus supplement.

New York Stock Exchange Symbol		“NMFC”

Investment Advisory Fees		We pay the Investment Adviser a fee for its services under an investment advisory and management agreement (the “Investment Management Agreement”) consisting of two components — a base management fee and an incentive fee. Pursuant to the Investment Management Agreement, the base management fee is calculated at an annual rate of 1.75% of our gross assets, which equals our total assets on the Consolidated Statements of Assets and Liabilities, less (i) the

S-9

		borrowings under the SLF Credit Facility and (ii) cash and cash equivalents. The base management fee is payable quarterly in arrears, and is calculated based on the average value of our gross assets, which equals our total assets, as determined in accordance with GAAP, less the borrowings under the SLF Credit Facility and cash and cash equivalents at the end of each of the two most recently completed calendar quarters, and appropriately adjusted on a pro rata basis for any equity capital raises or repurchases during the current calendar quarter. We have not invested, and currently do not invest, in derivatives. To the extent we invest in derivatives in the future, we will use the actual value of the derivatives, as reported on our Consolidated Statements of Assets and Liabilities, for purposes of calculating our base management fee. Since our IPO, the base management fee calculation has deducted the borrowings under the SLF Credit Facility. The SLF Credit Facility had historically consisted of primarily lower yielding assets at higher advance rates. As part of an amendment to our existing credit facilities with Wells Fargo Bank, National Association, the SLF Credit Facility merged with the Predecessor Holdings Credit Facility and into the Holdings Credit Facility on December 18, 2014. Post credit facility merger and to be consistent with the methodology since our IPO, the Investment Adviser will continue to waive management fees on the leverage associated with those assets that share the same underlying yield characteristics with investments leveraged under the legacy SLF Credit Facility. The Investment Adviser cannot recoup management fees that the Investment Adviser has previously waived. The incentive fee consists of two parts. The first part is calculated and payable quarterly in arrears and equals 20.0% of our “Pre-Incentive Fee Adjusted Net Investment Income” for the immediately preceding quarter, subject to a “preferred return”, or “hurdle”, and a “catch-up” feature each as described in the Investment Management Agreement. The second part will be determined and payable in arrears as of the end of each calendar year (or upon termination of the Investment Management Agreement) and will equal 20.0% of our “Adjusted Realized Capital Gains”, if any, on a cumulative basis from inception through the end of the year, computed net of all “Adjusted Realized Capital Losses” and “Adjusted Unrealized Capital Depreciation” on a cumulative basis, less the aggregate amount of any previously paid capital gain incentive fee each as described in the Investment Management Agreement. See “Investment Management Agreement” in the accompanying prospectus.

Administrator		The Administrator serves as our administrator and arranges our office space and provides us with office equipment and administrative services. The Administrator performs, or oversees the performance of, our financial records, prepares reports to our stockholders and reports filed by us with the SEC, monitors the payment of our expenses, and oversees the performance of administrative and professional services rendered to us by others. We reimburse the Administrator for our allocable portion of overhead and other expenses incurred by the Administrator in performing its obligations to us under an administration agreement, as amended and restated (the “Administration Agreement”). For the [ ] ended [ ], we incurred approximately $[ ] million of indirect administrative expenses, of which $[ ] million of indirect administrative expenses were waived by the Administrator. The Administrator cannot recoup any expenses that the Administrator has previously waived. For the [ ] ended [ ], we did not reimburse the Administrator for any indirect administrative expenses. See “Administration Agreement” in the accompanying prospectus.

Distributions		We intend to pay quarterly distributions to our stockholders out of assets legally

S-10

		available for distribution. The quarterly distributions, if any, will be determined by our board of directors. The distributions we pay to our stockholders in a year may exceed our taxable income for that year and, accordingly, a portion of such distributions may constitute a return of capital which is a return of a portion of a shareholder’s original investment in our common stock, for U.S. federal income tax purposes. Generally, a return of capital will reduce an investor’s basis in our stock for U.S. federal income tax purposes, which will result in a higher tax liability when the stock is sold. The specific tax characteristics of our distributions will be reported to stockholders after the end of the calendar year. See “Price Range of Common Stock and Distributions” in the accompanying prospectus.

Taxation of NMFC		We have elected to be treated, and intend to comply with the requirements to continue to qualify annually, as a RIC under Subchapter M of the Code. As a RIC, we generally will not pay corporate-level U.S. federal income taxes on any net ordinary income or capital gains that are timely distributed to our stockholders as dividends. To maintain our RIC status, we must meet specified source-of-income and asset diversification requirements and distribute annually to our stockholders at least 90.0% of our net ordinary income and realized net short-term capital gains in excess of realized net long-term capital losses, if any. See “Price Range of Common Stock and Distributions” and “Material Federal Income Tax Considerations” in the accompanying prospectus.

Dividend Reinvestment Plan		We have adopted an “opt out” dividend reinvestment plan for our stockholders. As a result, if we declare a distribution, then your cash distributions will be automatically reinvested in additional shares of our common stock, unless you specifically “opt out” of the dividend reinvestment plan so as to receive cash distributions. Stockholders who receive distributions in the form of stock will be subject to the same U.S. federal income tax consequences as stockholders who elect to receive their distributions in cash. We will use only newly issued shares to implement the plan if the price at which newly issued shares are to be credited is equal to or greater than 110.0% of the last determined net asset value of our shares. We reserve the right to either issue new shares or purchase shares of our common stock in the open market in connection with our implementation of the plan if the price at which newly issued shares are to be credited to stockholders’ accounts does not exceed 110.0% of the last determined net asset value of the shares. See “Dividend Reinvestment Plan” in the accompanying prospectus.

Trading at a Discount		Shares of closed-end investment companies frequently trade at a discount to their net asset value. The possibility that our common stock may trade at a discount to our net asset value per share is separate and distinct from the risk that our net asset value per share may decline. We cannot predict whether our common stock will trade above, at or below net asset value.

License Agreement		We have entered into a royalty-free license agreement with New Mountain Capital, pursuant to which New Mountain Capital has agreed to grant us a non-exclusive license to use the names “New Mountain” and “New Mountain Finance”. See “License Agreement” in the accompanying prospectus.

Leverage		We expect to continue to use leverage to make investments. As a result, we may continue to be exposed to the risks of leverage, which include that leverage may be considered a speculative investment technique. The use of leverage magnifies the potential for gain and loss on amounts we invest and therefore, indirectly, increases the risks associated with investing in shares of our common stock. See “Risk Factors” in the accompanying prospectus.

S-11

Anti-Takeover Provisions

Our board of directors is divided into three classes of directors serving staggered three-year terms. This structure is intended to provide us with a greater likelihood of continuity of management, which may be necessary for us to realize the full value of our investments. A staggered board of directors also may serve to deter hostile takeovers or proxy contests, as may certain other measures that we may adopt. These measures may delay, defer or prevent a transaction or a change in control that might otherwise be in the best interests of our stockholders. See “Description of NMFC’s Capital Stock—Delaware Law and Certain Certificate of Incorporation and Bylaw Provisions; Anti-Takeover Measures” in the accompanying prospectus.

Available Information

We have filed with the SEC a registration statement on Form N-2 together with all amendments and related exhibits under the Securities Act. The registration statement contains additional information about us and the shares of common stock being offered by this prospectus supplement and the accompanying prospectus.

We are required to file annual, quarterly and current reports, proxy statements and other information with the SEC under the Securities Exchange Act of 1934, as amended (the “Exchange Act”). This information is available at the SEC’s public reference room at 100 F Street, NE, Washington, District of Columbia 20549 and on the SEC’s website at http://www.sec.gov. The public may obtain information on the operation of the SEC’s public reference room by calling the SEC at 1-800-SEC-0330. This information is also available free of charge by contacting us at New Mountain Finance Corporation, 787 Seventh Avenue, 48th Floor, New York, New York 10019, by telephone at (212) 720-0300, or on our website at http://www.newmountainfinance.com. Information contained on our website or on the SEC’s web site about us is not incorporated into this prospectus supplement and the accompanying prospectus and you should not consider information contained on our website or on the SEC’s website to be part of this prospectus supplement and the accompanying prospectus.

FEES AND EXPENSES

The following table is intended to assist you in understanding the costs and expenses that you will bear directly or indirectly. We caution you that some of the percentages indicated in the table below are estimates and may vary. Except where the context suggests otherwise, whenever this prospectus supplement and the accompanying prospectus contains a reference to fees or expenses paid by “you”, “NMFC”, or “us” or that “we”, “NMFC”, or the “Company” will pay fees or expenses, we will pay such fees and expenses out of our net assets and, consequently, you will indirectly bear such fees or expenses as an investor in us. However, you will not be required to deliver any money or otherwise bear personal liability or responsibility for such fees or expenses.

Stockholder transaction expenses:
Sales load (as a percentage of offering price)			%(1)
Offering expenses borne by us (as a percentage of offering price)			%(2)
Dividend reinvestment plan fees			(3)
Total stockholder transaction expenses (as a percentage of offering price)			%
Annual expenses (as a percentage of net assets attributable to common stock):
Base management fees			%(4)
Incentive fees payable under the Investment Management Agreement			%(5)
Interest payments on borrowed funds			%(6)
Other expenses			%(7)
Acquired fund fees and expenses			%(8)
Total annual expenses			%(9)

S-12

Example

The following example, required by the SEC, demonstrates the projected dollar amount of total cumulative expenses that would be incurred over various periods with respect to a hypothetical investment in our common stock. In calculating the following expense amounts, we have assumed that our borrowings and annual operating expenses would remain at the levels set forth in the table above. See Note 6 below for additional information regarding certain assumptions regarding our level of leverage.

1
Year

3 Years

5 Years

10
Years

You would pay the following expenses on a $1,000 investment, assuming a 5.0% annual return

The example and the expenses in the tables above should not be considered a representation of future expenses, and actual expenses may be greater or less than those shown.

While the example assumes, as required by the applicable rules of the SEC, a 5.0% annual return, our performance will vary and may result in a return greater or less than 5.0%. The incentive fee under the Investment Management Agreement, which, assuming a 5.0% annual return, would either not be payable or would have an insignificant impact on the expense amounts shown above, is not included in the above example. The above illustration assumes that we will not realize any capital gains (computed net of all realized capital losses and unrealized capital depreciation) in any of the indicated time periods. If we achieve sufficient returns on our investments, including through the realization of capital gains, to trigger an incentive fee of a material amount, our expenses and returns to our investors would be higher. For example, if we assumed that we received our 5.0% annual return completely in the form of net realized capital gains on our investments, computed net of all cumulative unrealized depreciation on our investments, the projected dollar amount of total cumulative expenses set forth in the above illustration would be as follows:

1
Year

3 Years

5 Years

10
Years

You would pay the following expenses on a $1,000 investment, assuming a 5.0% annual return

The example assumes no sales load. In addition, while the examples assume reinvestment of all distributions at net asset value, participants in our dividend reinvestment plan will receive a number of shares of our common stock determined by dividing the total dollar amount of the distribution payable to a participant by the market price per share of our common stock at the close of trading on the dividend payment date. The market price per share of our common stock may be at, above or below net asset value. See “Dividend Reinvestment Plan” in the accompanying prospectus for additional information regarding the dividend reinvestment plan.

(1) Represents the commission with respect to the shares of our common stock being sold in this offering, which we will pay to in connection with sales of shares of our common stock effected by in this offering. There is no guaranty that there will be any sales of our common stock pursuant to this prospectus supplement and the accompanying prospectus.

(2) The offering expenses of this offering are estimated to be approximately $ .

(3) The de minimus expenses of the dividend reinvestment plan are included in “other expenses”.

(4) The base management fee under the Investment Management Agreement is based on an annual rate of [ ]% of our average gross assets for the two most recent quarters, which equals our total assets on the Consolidated Statements of Assets and Liabilities, less (i) the borrowings under the SLF Credit Facility and (ii) cash and cash equivalents. We have not invested, and currently do not invest, in derivatives. To the extent we invest in derivatives in the future, we will use the actual value of the derivatives, as reported on our Consolidated Statements of Assets and Liabilities, for purposes of calculating our base management fee. Since our IPO, the base

S-13

management fee calculation has deducted the borrowings under the SLF Credit Facility. The SLF Credit Facility had historically consisted of primarily lower yielding assets at higher advance rates. As part of an amendment to our existing credit facilities with Wells Fargo Bank, National Association, the SLF Credit Facility merged with the Predecessor Holdings Credit Facility and into the Holdings Credit Facility on December 18, 2014. Post credit facility merger and to be consistent with the methodology since our IPO, the Investment Adviser will continue to waive management fees on the leverage associated with those assets that share the same underlying yield characteristics with investments leveraged under the legacy SLF Credit Facility. The Investment Adviser cannot recoup management fees that the Investment Adviser has previously waived. The base management fee reflected in the table above is based on the [ ] ended [ ] and is calculated without deducting any management fees waived. The annual base management fee after deducting the management fee waiver as a percentage of net assets would be [ ]% based on the [ ] ended [ ]. See “Investment Management Agreement” in the accompanying prospectus.

(5) Assumes that annual incentive fees earned by the Investment Adviser remain consistent with the incentive fees earned by the Investment Adviser during the [ ] ended [ ] and includes accrued capital gains incentive fee. These accrued capital gains incentive fees would be paid by us if we ceased operations on [ ] and liquidated our investments at the [ ] valuation. As we cannot predict whether we will meet the thresholds for incentive fees under the Investment Management Agreement, the incentive fees paid in subsequent periods, if any, may be substantially different than the fees incurred during the [ ] ended [ ]. For more detailed information about the incentive fee calculations, see the “Investment Management Agreement” section of the accompanying prospectus.

(6) We may borrow funds from time to time to make investments to the extent we determine that additional capital would allow us to take advantage of additional investment opportunities or if the economic situation is otherwise conducive to doing so. The costs associated with these borrowings are indirectly borne by our stockholders. As of [ ], we had $[ ] million, $[ ] million, $[ ] million, $[ ] million and $[ ] million of indebtedness outstanding under the Holdings Credit Facility, the NMFC Credit Facility, the Convertible Notes, the Unsecured Notes and the SBA-guaranteed debentures, respectively. For purposes of this calculation, we have assumed the [ ] amounts outstanding under the credit facilities, Convertible Notes, Unsecured Notes and SBA-guaranteed debentures, and have computed interest expense using an assumed interest rate of [ ]% for the Holdings Credit Facility, [ ]% for the NMFC Credit Facility, [ ]% for the Convertible Notes, [ ]% for the Unsecured Notes and [ ]% for the SBA-guaranteed debentures, which were the rates payable as of [ ]. See “Senior Securities” in the accompanying prospectus.

(7) “Other expenses” include our overhead expenses, including payments by us under the Administration Agreement based on the allocable portion of overhead and other expenses incurred by the Administrator in performing its obligations to us under the Administration Agreement. Pursuant to the Administration Agreement, the Administrator may, in its own discretion, submit to us for reimbursement some or all of the expenses that the Administrator has incurred on our behalf during any quarterly period. As a result, the amount of expenses for which we will have to reimburse the Administrator may fluctuate in future quarterly periods and there can be no assurance given as to when, or if, the Administrator may determine to limit the expenses that the Administrator submits to us for reimbursement in the future. However, it is expected that the Administrator will continue to support part of our expense burden in the near future and may decide to not calculate and charge through certain overhead related amounts as well as continue to cover some of the indirect costs. The Administrator cannot recoup any expenses that the Administrator has previously waived. This expense ratio is calculated without deducting any expenses waived or reimbursed by the Administrator. Assuming the expenses waived or reimbursed by the Administrator at [ ], the annual expense ratio after deducting the expenses waived or reimbursed by the Administrator as a percentage of net assets would be [ ]%. For the [ ] ended [ ], we reimbursed our Administrator approximately $[ ] million, which represents approximately [ ]% of our net assets on an annualized basis. See “Administration Agreement” in the accompanying prospectus.

(8) The holders of shares of our common stock indirectly bear the expenses of our investment in NMFC Senior Loan Program I, LLC (“SLP I”) and NMFC Senior Loan Program II, LLC (“SLP II”). No management fee is charged on our investment in SLP I in connection with the administrative services provided to SLP I. As SLP II is structured as a private joint venture, no management fees are paid by SLP II. Future expenses for SLP I and SLP II may be substantially higher or lower because certain expenses may fluctuate over time.

(9) The holders of shares of our common stock indirectly bear the cost associated with our annual expenses.

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement contains forward-looking statements that involve substantial risks and uncertainties. These forward-looking statements are not historical facts, but rather are based on current expectations, estimates and projections about us, our current and prospective portfolio investments, our industry, our beliefs, and our assumptions. Words such as “anticipates,” “expects,” “intends,” “plans,” “believes,” “seeks,” “estimates,” “would,” “should,” “targets,” “projects,” and variations of these words and similar expressions are intended to identify forward-looking statements. The forward-looking statements contained in this prospectus supplement involve risks and uncertainties, including statements as to:

· our future operating results;

S-14

· ours business prospects and the prospects of our portfolio companies;

· the impact of investments that we expect to make;

· our contractual arrangements and relationships with third parties;

· the dependence of our future success on the general economy and its impact on the industries in which we invest;

· the ability of our portfolio companies to achieve their objectives;

· our expected financings and investments;

· the adequacy of our cash resources and working capital; and

· the timing of cash flows, if any, from the operations of our portfolio companies.

These statements are not guarantees of future performance and are subject to risks, uncertainties, and other factors, some of which are beyond our control and difficult to predict and could cause actual results to differ materially from those expressed or forecasted in the forward-looking statements, including without limitation:

· an economic downturn could impair our portfolio companies’ ability to continue to operate, which could lead to the loss of some or all of our investments in such portfolio companies;

· a contraction of available credit and/or an inability to access the equity markets could impair our lending and investment activities;

· interest rate volatility could adversely affect our results, particularly if we elect to use leverage as part of our investment strategy;

· currency fluctuations could adversely affect the results of our investments in foreign companies, particularly to the extent that we receive payments denominated in foreign currency rather than U.S. dollars; and

· the risks, uncertainties and other factors we identify in “Risk Factors” and elsewhere in this prospectus supplement, the accompanying prospectus and in our filings with the SEC.

Although we believe that the assumptions on which these forward-looking statements are based are reasonable, any of those assumptions could prove to be inaccurate, and as a result, the forward-looking statements based on those assumptions also could be inaccurate. Important assumptions include our ability to originate new loans and investments, certain margins and levels of profitability and the availability of additional capital. In light of these and other uncertainties, the inclusion of a projection or forward-looking statement in this prospectus supplement should not be regarded as a representation by us that our plans and objectives will be achieved. These risks and uncertainties include those described or identified in “Risk Factors” and elsewhere in this prospectus supplement and the accompanying prospectus. You should not place undue reliance on these forward-looking statements, which apply only as of the date of this prospectus supplement. However, we will update this prospectus supplement to reflect any material changes to the information contained herein. The forward-looking statements and projections contained in this prospectus supplement are excluded from the safe harbor protection provided by Section 27A of the Securities Act of 1933, as amended, or the Securities Act.

SELECTED FINANCIAL AND OTHER DATA

The selected financial data should be read in conjunction with the respective financial statements and related consolidated notes thereto and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” included in this prospectus supplement. Financial information for the years ended December 31, 20 , December 31, 20 , December 31, 20 , December 31, 20 and December 31, 20 has been derived from our

S-15

financial statements that were audited by [ ], an independent registered public accounting firm. The financial information at and for the [ ] months ended [ ], 20 was derived from our unaudited financial statements and related consolidated notes. In the opinion of management, all adjustments, consisting solely of normal recurring accruals, considered necessary for the fair presentation of financial statements for the interim periods, have been included. Our results for the interim periods may not be indicative of our results for any future interim period or the full year. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and “Senior Securities”, which are included elsewhere in this prospectus supplement and the accompanying in this prospectus, for more information.

[Insert Selected Financial and Other Data of New Mountain Finance Corporation reflecting most recently filed financials prior to the offering.]

CAPITALIZATION

The following table sets forth our capitalization as of [ ], 20[ ]:

· on an actual basis; and

· on an as adjusted basis to give effect to the sale of shares of our common stock in this offering at an assumed public offering price of $ per share (the last reported closing price of our common stock on , 20 ), after deducting the estimated underwriting discounts and commissions of approximately $ and estimated offering expenses of approximately $ payable by us.

You should read this table together with “Use of Proceeds” and financial statements and related notes thereto included elsewhere in this prospectus supplement and the accompanying prospectus.

	As of [ ], 20[ ]
	Actual	As Adjusted (unaudited)
	(in thousands)
Assets:
Cash and cash equivalents	$	$
Investments at fair value
Other assets
Total assets	$	$

Liabilities:
Credit facilities payable	$	$
Other liabilities
Total liabilities	$	$
Net assets	$	$

Stockholders’ equity:
Common stock, par value $0.01 per share; 100,000,000 shares authorized,shares outstanding		$
Capital in excess of par value		$
Total stockholders’ equity		$

USE OF PROCEEDS

We estimate that we will receive net proceeds from the sale of the shares of our common stock in this offering of approximately $ million, or approximately $ million if the underwriters exercise their option to purchase additional shares in full (in each case using the last reported closing price of our common stock on , 20 of $ per share), after deducting estimated offering expenses of approximately $ payable by us.

S-16

We intend to use the net proceeds from this offering for new investments in portfolio companies in accordance with our investment objective and strategies described in this prospectus supplement and the accompanying prospectus, to temporarily repay indebtedness (which will be subject to reborrowing), to pay our operating expenses, to pay distributions to our stockholders/unit holders and for general corporate purposes. We are continuously identifying, reviewing and, to the extent consistent with its investment objective, funding new investments. As a result, we typically raise capital as we deem appropriate to fund such new investments.

We estimate that it will take to months for us to substantially invest the net proceeds of this offering, depending on the availability of attractive opportunities and market conditions. However, we can offer no assurance that we will be able to achieve this goal.

Proceeds not immediately used for new investments or the temporary repayment of debt will be invested primarily in cash, cash equivalents, U.S. government securities and other high-quality investments that mature in one year or less from the date of investment. These temporary investments are expected to provide a lower net return than we hope to achieve from our target investments.

MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The information contained in this section should be read in conjunction with the Selected Financial and Other Data and our Financial Statements and notes thereto appearing elsewhere in this prospectus supplement. For the periods prior to and as of December 31, 2013, all financial information provided in this prospectus reflects our organizational structure prior to the restructuring on May 8, 2014 described under “Description of Restructuring” in the accompanying prospectus supplement, where NMF Holdings functioned as the operating company. In addition to historical information, the following discussion and other parts of this prospectus contain forward-looking information that involves risks and uncertainties. Our actual results could differ materially from those anticipated by such forward-looking information due to the factors discussed under “Risk Factors” and “Cautionary Statement Regarding Forward-Looking Statements” appearing elsewhere in this prospectus supplement and the accompanying prospectus.

[Insert Management’s Discussion and Analysis of Financial Condition and Results of Operations from most recently filed Quarterly Report on Form 10-Q or Annual Report on Form 10-K, as applicable, prior to the offering.]

PRICE RANGE OF COMMON STOCK

Our common stock is traded on the New York Stock Exchange (“NYSE”) under the symbol “NMFC”. The following table sets forth, for each fiscal quarter during the last two fiscal years and the current fiscal year to date, the net asset value (“NAV”) per share of our common stock, the high and low closing sale price for our common stock, the closing sale price as a percentage of NAV and the quarterly distributions per share.

[Insert Price Range of Common Stock at the time of offering.]

S-17

On [ ], the last reported sales price of our common stock was $[ ] per share. As of [ ], we had approximately [ ] stockholders of record and approximately one beneficial owner whose shares are held in the names of brokers, dealers, funds, trusts and clearing agencies.

Shares of BDCs may trade at a market price that is less than the value of the net assets attributable to those shares. The possibility that our shares of common stock will trade at a discount from NAV or at premiums that are unsustainable over the long term are separate and distinct from the risk that our NAV will decrease. Since our initial public offering on May 19, 2011, our shares of common stock have traded at times at both a discount and a premium to the net assets attributable to those shares. As of [ ], our shares of common stock traded at a premium of approximately [ ]% of the NAV attributable to those shares as of [ ]. It is not possible to predict whether the shares offered hereby will trade at, above, or below NAV.

We intend to pay quarterly distributions to our stockholders in amounts sufficient to maintain our status as a RIC. We intend to distribute approximately our entire Adjusted Net Investment Income (defined as net investment income adjusted to reflect income as if the cost basis of investments held at the IPO date had stepped-up to fair market value as of the IPO date) on a quarterly basis and substantially all of our taxable income on an annual basis, except that we may retain certain net capital gains for reinvestment.

We maintain an “opt out” dividend reinvestment plan on behalf of our stockholders, pursuant to which each of our stockholders’ cash distributions will be automatically reinvested in additional shares of our common stock, unless the stockholder elects to receive cash.

We apply the following in implementing the dividend reinvestment plan. If the price at which newly issued shares are to be credited to stockholders’ accounts is equal to or greater than 110.0% of the last determined NAV of the shares, we will use only newly issued shares to implement the dividend reinvestment plan. Under such circumstances, the number of shares to be issued to a stockholder is determined by dividing the total dollar amount of the distribution payable to such stockholder by the market price per share of our common stock on the NYSE on the distribution payment date. Market price per share on that date will be the closing price for such shares on the NYSE or, if no sale is reported for such day, the average of their electronically reported bid and ask prices.

If the price at which newly issued shares are to be credited to stockholders’ accounts is less than 110.0% of the last determined NAV of the shares, we will either issue new shares or instruct the plan administrator to purchase shares in the open market to satisfy the additional shares required. Shares purchased in open market transactions by the plan administrator will be allocated to a stockholder based on the average purchase price, excluding any brokerage charges or other charges, of all shares of common stock purchased in the open market. The number of shares of our common stock to be outstanding after giving effect to payment of the distribution cannot be established until the value per share at which additional shares will be issued has been determined and elections of our stockholders have been tabulated.

The following table reflects the cash distributions, including dividends and returns of capital, if any, per share that have been declared by our board of directors for the two most recent fiscal years and the current fiscal year to date:

[Insert Distributions at the time of offering.]

S-18

The underwriters are committed to take and pay for all of the shares being offered, if any are taken, other than the shares covered by the option described below unless and until this option is exercised.

If the underwriters sell more shares than the total number set forth in the table above, the underwriters have an option to buy up to an additional [ ] shares from us. They may exercise that option for [ ] days. If any shares are purchased pursuant to this option, the underwriters will severally purchase shares in approximately the same proportion as set forth in the table above.

The following table shows the per share and total underwriting discounts and commissions (sales load) to be paid to the underwriters by us. Such amounts are shown assuming both no exercise and full exercise of the underwriters’ option to purchase [ ] additional shares. This offering will conform with the requirements set forth in Financial Industry Regulatory Authority Rule 2310. In compliance with such requirements, the underwriting discounts and commissions in connection with the sale of securities will not exceed 10% of gross proceeds of this offering.

	No Exercise	Full Exercise
Per Share	$	$
Total	$	$

Shares sold by the underwriters to the public will initially be offered at the public offering price set forth on the cover of this prospectus supplement. Any shares sold by the underwriters to securities dealers may be sold at a discount of up to $ per share from the public offering price. If all the shares are not sold at the initial offering price, the representatives may change the public offering price and the other selling terms. The offering of the shares by the underwriters is subject to receipt and acceptance and subject to the underwriters’ right to reject any order in whole or in part.

We, each of our officers and directors, and each of the members of the Investment Adviser’s investment committee have agreed with the underwriters, subject to certain exceptions, not to dispose of or hedge any shares of our common stock or securities convertible into or exchangeable for shares of our common stock during the period from the date of this prospectus supplement continuing through the date [ ] days after the date of this prospectus supplement, except with the prior written consent of [ ].

Our common stock is listed on the New York Stock Exchange under the symbol “NMFC”.

In connection with the offering, the underwriters may purchase and sell shares of common stock in the open market. These transactions may include short sales, stabilizing transactions and purchases to cover positions created by short sales. Short sales involve the sale by the underwriters of a greater number of shares than they are required to purchase in the offering. “Covered” short sales are sales made in an amount not greater than the underwriters’ option to purchase additional shares from us in the offering. The underwriters may close out any covered short position by either exercising their option to purchase additional shares or purchasing shares in the open market. In determining the source of shares to close out the covered short position, the underwriters will consider, among other things, the price of shares available for purchase in the open market as compared to the price at which they may purchase additional shares pursuant to the option granted to them. “Naked” short sales are any sales in excess of such option. The underwriters must close out any naked short position by purchasing shares in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the common stock in the open market after pricing that could adversely affect investors who purchase in the offering. Stabilizing transactions consist of various bids for or purchases of common stock made by the underwriters in the open market prior to the completion of the offering.

The underwriters may also impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discount received by it because the representatives have repurchased shares sold by or for the account of such underwriter in stabilizing or short covering transactions.

Purchases to cover a short position and stabilizing transactions, as well as other purchases by the underwriters for their own account, may have the effect of preventing or retarding a decline in the market price of the company’s stock, and together with the imposition of the penalty bid, may stabilize, maintain or otherwise affect the market price of the common stock. As a result, the price of the common stock may be higher than the price that otherwise

S-20

might exist in the open market. If these activities are commenced, they may be discontinued at any time. These transactions may be effected on the New York Stock Exchange, in the over-the-counter market or otherwise.

The underwriters do not expect sales to discretionary accounts to exceed five percent of the total number of shares offered.

We estimate that our share of the total expenses of the offering, excluding underwriting discounts and commissions, will be approximately $[ ]. We will pay all of the expenses incurred by us in connection with this offering.

We have agreed to indemnify the several underwriters against certain liabilities, including liabilities under the Securities Act of 1933.

The underwriters and their respective affiliates are full-service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. Certain of the underwriters and their respective affiliates may, from time to time, perform various financial advisory and investment banking services for the company, for which they will receive customary fees and expenses.

In the ordinary course of their various business activities, the underwriters and their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers and such investment and securities activities may involve securities and/or instruments of the issuer. The underwriters and their respective affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

The principal business address of [ ], [ ], [ ], [ ] [ ].

Each of the underwriters may arrange to sell common shares offered hereby in certain jurisdictions outside the United States, either directly or through affiliates, where they are permitted to do so.

[Describe any other specific transactions and compensation related thereto to the extent required to be disclosed by applicable law or regulation.]

[Insert applicable legends for jurisdictions in which offers and sales may be made.]

LEGAL MATTERS

Certain legal matters in connection with the securities offered hereby will be passed upon for us by Eversheds Sutherland (US) LLP, Washington, District of Columbia. Certain legal matters in connection with the securities offered hereby will be passed upon for the underwriters by , , .

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

[Insert financial information at the time of offering.]

S-21

The principal business address of Deloitte & Touche LLP is 30 Rockefeller Center Plaza, New York, New York 10112.

AVAILABLE INFORMATION

We have filed with the SEC a registration statement on Form N-2, together with all amendments and related exhibits, under the Securities Act, with respect to the shares of common stock offered by this prospectus supplement and the accompanying prospectus. The registration statement contains additional information about us and the shares of common stock being offered by this prospectus supplement and the accompanying prospectus.

We are required to file with or submit to the SEC annual, quarterly and current reports, proxy statements and other information meeting the informational requirements of the Exchange Act. You may inspect and copy these reports, proxy statements and other information, as well as the registration statement and related exhibits and schedules, at the Public Reference Room of the SEC at 100 F Street, N.E., Washington, District of Columbia 20549. You may obtain information on the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330. The SEC maintains an internet site that contains reports, proxy and information statements and other information filed electronically by us with the SEC, which are available on the SEC’s website at http://www.sec.gov. Copies of these reports, proxy and information statements and other information may be obtained, after paying a duplicating fee, by electronic request at the following e-mail address: publicinfo@sec.gov, or by writing the SEC’s Public Reference Section, 100 F Street, N.E., Washington, District of Columbia 20549. This information will also be available free of charge by contacting us at 787 Seventh Avenue, 48th Floor, New York, New York 10019, by telephone at (212) 720-0300, or on our website at http://www.newmountainfinance.com. Information contained on our website or on the SEC’s web site about us is not incorporated into this prospectus supplement and the accompanying prospectus and you should not consider information contained on our website or on the SEC’s website to be part of this prospectus supplement and the accompanying prospectus.

S-22

Underwriter		Number of Shares




Total