UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): June 5, 2013

OREXIGEN THERAPEUTICS, INC.

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (858) 875-8600

(Former Name or Former Address, if Changed Since Last Report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensation Arrangements of Certain Officers.

On June 5, 2013, at the 2013 annual meeting of stockholders of Orexigen Therapeutics, Inc. (the “Company” or “Orexigen”), the Company’s stockholders approved the Company’s 2013 Employee Stock Purchase Plan (the “ESPP”), the purpose of which plan is (i) to provide a means by which Company employees (and employees of any parent or subsidiary of the Company designated by the Company’s board of directors to participate in the ESPP) be given an opportunity to use payroll deductions for the purchase of our common stock at a discount from fair market value (the lower of (a) 85% of the fair market value of a share of common stock on the first day of the applicable offering period or (b) 85% of the fair market value of a share of common stock on the purchase date (i.e., the last day of the applicable six-month purchase period)), (ii) to assist the Company in retaining the services of its employees, (iii) to secure and retain the services of new employees, and (iv) to provide incentives for such persons to exert maximum efforts for the success of the Company and its affiliates. An aggregate of 6,000,000 shares of common stock is reserved for issuance under the ESPP.

A description of the material terms of the Company’s ESPP is set forth on pages 18-22 of the Company’s Definitive Proxy Statement on Schedule 14A for the 2013 annual meeting, which was filed with the Securities and Exchange Commission (“SEC”) on April 23, 2013 and is incorporated herein by reference. That summary and the foregoing description of the ESPP are qualified in their entirety by reference to the text of the ESPP, which was filed as Exhibit 10.1 to the Company’s Form S-8 filed with the SEC on June 6, 2013 and is incorporated herein by reference.

Item 5.07 Submission of Matters to a Vote of Security Holders.

The Company held its annual meeting of stockholders on June 5, 2013. The following is a brief description of each matter voted upon at the meeting and the number of votes cast for, withheld or against, the number of abstentions and the numbers of broker non-votes with respect to each matter, as applicable.

In accordance with the above results, each nominee was elected to serve as a director.

In accordance with the above results, the Orexigen Therapeutics, Inc. 2013 Employee Stock Purchase Plan was approved.

In accordance with the above results, the appointment of Ernst & Young LLP was approved.

(d) Exhibits

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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