Item 12(a)(1)

THORNBURG INVESTMENT TRUST

CODE OF BUSINESS CONDUCT AND ETHICS

September 10, 2003

as revised to December 6, 2009

Introduction

Honesty and integrity are hallmarks of Thornburg Investment Trust (the “Trust”). We pride ourselves on maintaining the highest standards of ethics and conduct in all of our business relationships. This Code of Business Conduct and Ethics covers a wide range of business practices and procedures and applies to the officers and Trustees of the Trust in their conduct of the business and affairs of the Trust. It does not cover every issue that may arise, but it sets out basic principles to guide the officers and Trustees of the Trust in discharging their duties for the Trust. This Code has been adopted by the Trustees of the Trust with the objectives of deterring wrongdoing and promoting (1) honest and ethical conduct, including the ethical handling of actual or apparent conflicts of interest between personal and professional relationships, (2) full, fair, accurate, timely and understandable disclosure in reports and documents which the Trust files with the Securities and Exchange Commission and in other public communications made by the Trust, (3) compliance with applicable governmental laws, rules and regulations, (4) prompt internal reporting of violations of this Code, and (5) accountability for adherence to this Code.

This Code is intended as a code of ethics under Section 406 of the Sarbanes-Oxley Act of 2002 and Item 2 of Form N-CSR under the Investment Company Act of 1940, and is specifically applicable to the principal executive officer, principal financial officer, and principal accounting officer (or persons performing similar functions, whether or not as officers or employees of the Trust) of the Trust (each a “Covered Officer”).

All records and reports created or maintained pursuant to this Code are intended solely for the internal use of the Trust, are confidential, and in no event constitute an admission by any person as to any fact, circumstance or legal conclusion.

Compliance with Laws, Rules and Regulations

The Trust expects its officers and Trustees to comply with all laws, rules and regulations applicable to the Trust’s operations and business. Officers and Trustees should seek guidance whenever they are in doubt as to the applicability of any law, rule or regulation regarding any contemplated course of action. The Trust and its investment adviser hold information and training sessions to promote compliance with laws, rules and regulations, including insider-trading laws. Please consult the various guidelines and policies which the Trust has prepared in accordance with specific laws and regulations. A good guideline, if in doubt on a course of action, is “Always ask first, act later — if you are unsure of what to do in any situation, seek guidance before you act.”

As a registered investment company, we are subject to regulation by the Securities and Exchange Commission, and compliance with federal, state and local laws. The Trust and its Trustees insist on strict compliance with the spirit and the letter of these laws and regulations.

Conflicts of Interest

Each officer and Trustee of the Trust should be scrupulous in avoiding any conflict of interest or appearance of such a conflict with regard to the Trust’s interests. A “conflict of interest” occurs when an individual’s private interest interferes with the interests of the Trust. The appearance of a conflict occurs for purposes of this Code when an individual enters into a transaction, has a relationship with or receives a benefit from a third party, or engages in any other conduct, which would cause an unrelated observer to reasonably conclude that an actual conflict exists. A conflict may arise when an officer or Trustee pursues interests that prevent the individual from performing his duties to the Trust objectively and effectively. A conflict also may arise when an officer or Trustee or member of the individual’s family receives undisclosed, improper benefits as a result of the individual’s position with the Trust. The appearance of a conflict may arise when an individual or his family member has a relationship with a person who does business with the Trust or its investment adviser. Any conflict of interest that arises in a specific situation or transaction must be disclosed by the individual and resolved before taking any action.

Matters involving a conflict of interest or appearance of a conflict are prohibited as a matter of Trust policy, except when approved by the Trustees or the Trust’s audit committee for any Covered Officer or Trustee, or except when approved by the Trust’s president for any other individual. Conflicts of interest may not always be evident, and individuals should consult with higher levels of management or the Trust’s legal counsel if they are uncertain about any situation. In no event, however, shall investment in any security made in accordance with the Trust’s Policy on Personal Securities Transactions (or comparable policy or code then in effect) be considered a conflict of interest with the Trust.

Corporate Opportunities

Officers and Trustees shall not take for themselves personally opportunities that are discovered through the use of their position with the Trust, except with the approval of the Trustees or the Trust’s audit committee for any Covered Officer or Trustee, or except with the approval by the Trust’s president for any other individual. Officers and Trustees owe a duty to the Trust to advance its legitimate interests when the opportunity to do so arises. In no event, however, shall investment in any security made in accordance with the Trust’s Policy on Personal Securities Transactions (or comparable policy or code then in effect) be considered a business opportunity of the Trust.

Confidentiality

Officers and Trustees shall exercise care in maintaining the confidentiality of any confidential information respecting the Trust, except where disclosure is authorized or legally mandated. Officers and Trustees should consult with the Trust’s legal counsel if they believe they have a legal obligation to disclose confidential information. Confidential information includes non-public information of the Trust that may be helpful to competitors, or otherwise harmful to the Trust or its shareholders. The obligation to preserve confidentiality of this information continues after association with the Trust ends.

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Fair Dealing

Officers and Trustees should endeavor to deal fairly with the Trust’s shareholders, service providers and competitors, and shall not seek unfair advantage through improper concealment, abuse of improperly acquired confidential information, misrepresentation of material facts when the other party is known by the officer or Trustee to rely justifiably on the individual to disclose those facts truthfully, or improper and unfair dealing.

Business Gifts and Entertainment

The purpose of business entertainment and gifts in a commercial setting is to create goodwill and sound working relationships, not to gain unfair advantage. No gift or entertainment should ever be offered, given, provided or accepted by any officer or Trustee in connection with the Trust’s business unless it (1) is not a cash gift, (2) is consistent with customary business practices, (3) is not excessive in value, (4) cannot be construed as a bribe, payoff or kickback and (5) does not violate any laws or regulations.

Protection and Proper Use of Trust Assets

All officers and Trustees should endeavor to protect the Trust’s assets and pursue their efficient investment in accordance with the Trust’s business purposes and declaration of trust. Any suspected incident of fraud or theft should be immediately reported for investigation.

The obligation of officers and Trustees to protect the Trust’s assets includes its proprietary information. Proprietary information includes intellectual property such as trademarks and copyrights, as well as business, marketing and service plans, databases, records, salary information and any unpublished financial data and reports. Unauthorized use or distribution of this information violates this Code.

Insider Trading

All officers and Trustees should pay particular attention to potential violations of insider trading laws. Insider trading is both unethical and illegal and will be dealt with decisively if it occurs. Officers and Trustees are expected to familiarize themselves with the Policy Statement on Insider Trading, adopted by the Trust’s investment adviser. If they have questions about these guidelines, they should consult with the Trust’s president, the investment adviser’s compliance office, or the Trust’s legal counsel.

Certain Political Contributions Proscribed

Contributions or solicitations for contributions, by any officer or Trustee of the Trust who is an employee, officer or director of the Trust’s investment advisor or distributor, to any political campaign in which an independent Trustee is a candidate, are prohibited. This prohibition does not apply to (i) a contribution by an independent Trustee to a political campaign of another independent Trustee, or (ii) a solicitation by an independent Trustee for the political campaign of another independent Trustee if the solicitation is made to an individual with whom the soliciting Trustee has some relationship, or to an individual who either has a relationship with the candidate Trustee or who would be expected to have an interest in the outcome of the campaign.

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Reporting Illegal or Unethical Behavior

The Trustees encourage each officer to talk to senior officers, the investment adviser’s compliance officers, or the Trustees about observed illegal or unethical behavior, or when the officer is in doubt about the best course of action in a particular situation. Officers should report actual and suspected violations of laws, rules, regulations or this Code to appropriate personnel. If an individual does not believe it appropriate or is not comfortable approaching senior officers or the investment adviser’s compliance officers about their concerns, then the individual may contact any member of the Trust’s audit committee. If the individual’s concerns require confidentiality, then this confidentiality will be protected, subject to applicable law, regulation or legal proceedings. The Trust will not permit retaliation of any kind by or on behalf of the Trust or its officers and Trustees against good faith reports or complaints of violations of this Code or other illegal or unethical conduct.

Reporting and Disclosure

As a registered investment company, it is of critical importance that the Trust’s filings with the Securities and Exchange Commission contain full, fair, accurate, timely and understandable disclosure. Each officer and Trustee should become familiar with the disclosure laws and regulations applicable to the Trust, consistent with the individual’s authority and duties. Depending on the Trust, each officer and Trustee may be called upon to provide necessary information to ensure that the Trust’s public reports are complete, fair and understandable. The Trustees expect officers and Trustees to take this responsibility very seriously and to provide prompt and accurate answers to inquiries related to the Trust’s public disclosure requirements. Officers may be asked to certify as to the accuracy of all responses and information provided for inclusion in the Trust’s public reports and filings.

Recordkeeping

The Trust requires accurate recording and reporting of information in order to make responsible business decisions. The Trustees expect each of the Trust’s officers, consistent with the officer’s individual authority and duties, to maintain the Trust’s books, records, accounts and financial statements in reasonable detail, and to appropriately reflect the Trust’s transactions in conformity with applicable legal requirements and the Trust’s system of internal controls.

Accounting and Financial Reporting Concerns

The Trust seeks to comply with all applicable financial reporting and accounting regulations applicable to the Trust. Officers who have concerns or complaints regarding questionable accounting or auditing matters or procedures involving the Trust are encouraged to submit those concerns or complaints to the Trust’s audit committee which will, subject to its duties arising under applicable law, regulations and legal proceedings, treat such submissions confidentially. These submissions may be directed to the attention of the audit committee chairman, or any Trustee who is a member of the audit committee, at the principal executive offices of the Trust or at the Trustee’s residence address.

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Waivers of the Code of Business Conduct and Ethics

Any waiver of this Code for any Covered Officer or Trustee may be made only by the Trustees or the Trust’s audit committee and will be promptly disclosed as required by law or by Securities and Exchange Commission regulations. Waivers of this Code for any other individual may be made by the president only upon the individual’s making full disclosure in advance of the transaction in question. This Code may be amended or modified at any time by the Trustees.

History: Approved and adopted by Trustees of Thornburg Investment Trust on September 10, 2003, effective the same date; amended effective July 20, 2005 to revise provisions respecting conflicts of interest; amended effective December 6, 2009 to add a paragraph respecting campaign contributions.

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