The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F COVER PAGE

OMB APPROVAL
OMB Number: 3235-0006
Estimated average burden
hours per response: 23.8

Report for the Calendar Year or Quarter Ended: 06-30-2018
Check here if Amendment    Amendment Number:
This Amendment (Check only one.):    is a restatement.
   adds new holdings entries.
Institutional Investment Manager Filing this Report:
Name: SEI INVESTMENTS CO
Address: 1 FREEDOM VALLEY DRIVE
OAKS, PA  19456-1100
Form 13F File Number: 028-16454

The institutional investment manager filing this report and the person by whom it is signed hereby represent that the person signing the report is authorized to submit it, that all information contained herein is true, correct and complete, and that it is understood that all required items, statements, schedules, lists, and tables, are considered integral parts of this form.

Person Signing this Report on Behalf of Reporting Manager:
Name: Michael N. Peterson
Title: Executive Vice President
Phone: 610-676-1000
Signature, Place, and Date of Signing:
Michael N. Peterson OaksPA 08-02-2018
[Signature] [City, State] [Date]
SEI Investments Company (SEI) is the parent holding company of certain institutional investment managers, as defined by Section 13(f) of the Securities Exchange Act of 1934, as amended (the "Act"). For purposes of the reporting requirements under Section 13(f) of the Act, and the rules promulgated thereunder, SEI does not exercise, and therefore disclaims, investment discretion with respect to any Section 13(f) securities positions over which its investment operating subsidiaries exercise such discretion. To the extent, however, that SEI's ownership interest in such subsidiaries may nevertheless give rise to a Form 13F obligation for SEI, the information required by Form 13F is reported herein on behalf of the following subsidiaries: SEI Investments Management Corporation ("SIMC"), SEI Trust Company and SEI Investments Canada Company (SEI Canada). Voting authority with respect to the Section 13(f) securities reported herein resides with and is exercised by SEI's operating subsidiaries, unless otherwise indicated. Although SEI has not been delegated voting authority over such Section 13(f) securities, and disclaims such voting authority, pursuant to instruction 12b.viii of Form 13F, and for that purpose only, such Section 13(f) securities are reported as "Sole Voting Authority." SIMC and SEI Canada each serve as an investment adviser to a number of pooled investment vehicles, which may include mutual funds, hedge funds, private equity funds, collective investment trusts and offshore investment funds (together, the "Pooled Investment Vehicles"). In addition, SIMC sponsor and may serve as adviser to, separately managed account programs (SMA Programs) . SIMC and SEI Canada may act as a "manager of managers" whereby each retain, subject to SIMC's and SEI Canada's oversight, respectively, sub-advisers to buy and sell securities on behalf of such Pooled Investment Vehicles and SMA Programs. To the extent that SIMC's and SEI Canada's role as a manager of managers could give rise to a Form 13F obligation, SIMC or SEI Canada has instructed its sub-advisers to file a Form 13F with respect to such securities and has included such sub-advisers in the "list of other managers reporting for this manager" below.
Report Type (Check only one.):
   13F HOLDINGS REPORT. (Check here if all holdings of this reporting manager are reported in this report.)
   13F NOTICE. (Check here if no holdings reported are in this report, and all holdings are reported by other reporting manager(s).)
X 13F COMBINATION REPORT. (Check here if a portion of the holdings for this reporting manager are reported in this report and a portion are reported by other reporting manager(s).)
List of Other Managers Reporting for this Manager:
[If there are no entries in this list, omit this section.]
Form 13F File Number Name
028-11685 1832 Asset Management L.P.
028-05990 Acadian Asset Management LLC
028-05508 AJO, LP
028-10562 AllianceBernstein L.P.
028-04895 Analytic Investors, LLC
028-10120 AQR Capital Management LLC
028-17137 Arcus
028-12990 Ares Management LLC
028-13791 ArrowMark Partners
028-05615 Axiom International Investors
028-18146 Benefit Street Partners
028-02951 Beutel Goodman Capital Management
028-12820 Brigade Capital Management, LP
028-18355 Caerus Investors, LLC
028-05573 CastleArk Management LLC
028-11728 Causeway
028-05577 CenterSquare Investment Management Inc
028-11563 Coho Partners
028-14070 EAM Investors, LLC
028-10492 Falcon Point Capital
028-14036 Fiera Capital Corp.
028-12836 Guggenheim Capital Llc
028-12180 Hexavest Inc.
028-11957 Hillsdale Investment Management Inc.
028-04211 Intech Investment Management LLC
028-11119 Integrity Asset Management, LLC
028-12634 Investec Asset Management Ltd.
028-16230 Jackson Square Partners Ltd
028-11937 JP Morgan Investment Management
028-17689 Kettle Hill Capital Management, LLC
028-13048 KBI Global Investors Ltd
028-10469 Lazard Asset Management Ltd
028-13608 LMCG Investments, LLC
028-06580 LSV Asset Management
028-13124 Macquarie Investment Management
028-03673 ManuLife Asset Management LLC
028-17488 Maple-Brown Abbott
028-13628 Montrusco Bolton Investments Inc.
028-13573 Neuberger Berman Group LLC
028-01474 NWQ Investment Management Company, LLC
028-00203 OppenheimerFunds Inc.
028-03042 PanAgora Asset Management Inc.
028-04558 Parametric Portfolio Associates LLC
028-12690 PCJ Investment Counsel Ltd
028-14009 QS Investors LLC
028-11173 Quantiative Management Associates
028-10674 Ramius Advisors LLC
028-10467 Rice Hall James
028-14481 RWC Asset Management LLP
028-07312 Security Capital Research & Management Inc
028-10613 Snow Capital Management LP
028-11300 Spectrum Asset Management, Inc.
028-00733 State Street Bank & Trust
028-10640 Towle & Co
028-07104 WCM Investment Management/CA
028-17022 William Blair & Co
Form 13F Summary Page
Report Summary:
Number of Other Included Managers: 12
Form 13F Information Table Entry Total: 7,559
Form 13F Information Table Value Total: 29,421,570
(thousands)
List of Other Included Managers:
Provide a numbered list of the name(s) and Form 13F file number(s) of all institutional investment managers with respect to which this report is filed, other than the manager filing this report.
[If there are no entries in this list, state “NONE” and omit the column headings and list entries.]
No. Form 13F File Number Name
1 028-16475 SEI Investment Management Corporation
2 028-10297 SEI Trust Company
3 028-16449 SEI Investments Canada Company
4   SEI Huntington Steele, LLC
5   Blackcrane Capital LLC
6   Ceredex Value Advisors LLC
7   EAM Investors LLC
8   EARNEST Partners LLC
9   Fondsmaeglerselskabet Maj Invest A/S
10   Jupiter Asset Management Ltd
11   Mountaineer
12   Sionna Investment Managers Inc.