UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 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): January 23, 2014

XENOPORT, INC.

(Exact name of registrant as specified in its charter)

3410 Central Expressway

Santa Clara, California 95051

(Address of Principal Executive Offices) (Zip Code)

Registrant’s telephone number, including area code: (408) 616-7200

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:

Section 8 – Other Events

Item 8.01 Other Events.

On January 23, 2014, XenoPort, Inc. (“XenoPort,” “we,” “our” or “us”) entered into an underwriting agreement (the “Underwriting Agreement”) with Credit Suisse Securities (USA) LLC, as representative of the several underwriters named therein (collectively, the “Underwriters”), relating to the issuance and sale of 12,000,000 shares of our common stock, par value $0.001 per share. The size of the offering was increased from the 10,000,000 shares initially announced. The price to the public in this offering is $6.00 per share and the Underwriters have agreed to purchase the shares from us pursuant to the Underwriting Agreement at a price of $5.655 per share. The net proceeds to us from this offering are expected to be approximately $67.3 million, after deducting the underwriting discounts and commissions and other estimated offering expenses payable by us. The closing of the offering is expected to take place on or about January 29, 2014, subject to customary closing conditions. In addition, under the terms of the Underwriting Agreement, we have granted the Underwriters an option, exercisable for 30 days from January 23, 2014, to purchase up to an additional 1,800,000 shares of our common stock.

The Underwriting Agreement contains customary representations, warranties and agreements by us, customary conditions to closing, indemnification obligations of XenoPort and the Underwriters, including for liabilities under the Securities Act of 1933, as amended, other obligations of the parties and termination provisions. The representations, warranties and covenants contained in the Underwriting Agreement were made only for purposes of such agreement and as of specific dates, were solely for the benefit of the parties to such agreement, and may be subject to limitations agreed upon by the contracting parties.

The offering is being made pursuant to a registration statement on Form S-3 previously filed with and declared effective by the Securities and Exchange Commission (the “SEC”) and a prospectus supplement thereunder. A copy of the Underwriting Agreement is filed as Exhibit 1.1 to this report, and the foregoing description of the Underwriting Agreement does not purport to be complete and is qualified in its entirety by reference to such exhibit. A copy of the opinion of Cooley LLP relating to the validity of the issuance and sale of the common stock in the offering is attached as Exhibit 5.1 hereto.

Forward-Looking Statements

This report contains “forward-looking” statements, including, without limitation, all statements related to the completion, timing and size of the offering. Any statements contained in this report that are not statements of historical fact may be deemed to be forward-looking statements. Words such as “expected” and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based upon XenoPort’s current expectations. Forward-looking statements involve risks and uncertainties. XenoPort’s actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, risks and uncertainties associated with market conditions, whether XenoPort will be able to consummate the offering. There can be no assurance that XenoPort will be able to complete the offering. Regardless of whether the offering is consummated, XenoPort will continue to need additional funding and may be unable to raise capital when needed, which would force XenoPort to delay, reduce or eliminate its product development programs or commercialization efforts. These and other risk factors related to XenoPort and its business are discussed under the heading “Risk Factors” in the preliminary prospectus supplement related to the offering filed with the SEC on January 21, 2014. XenoPort expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in XenoPort’s expectations with regard thereto or any change in events, conditions or circumstances on which any such statements are based.

Item 9.01 Financial Statements and 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.

EXHIBIT INDEX