UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K/A

(Amendment No. 1)

For the Fiscal Year Ended December 31, 2009

OR

For the transition period from                      to                     

Commission file number: 001-32836

MEDIVATION, INC.

(Exact name of Registrant as specified in its charter)

525 Market Street, 36^th Floor

San Francisco, California 94105

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (415) 543-3470

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    YES  x    NO  ¨

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.    YES  ¨    NO  x

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports) and (2) has been subject to such filing requirements for the past 90 days.    YES  x    NO  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    YES  ¨    NO  ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.  x

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act.).    YES  ¨    NO  x

The aggregate market value of the voting stock held by non-affiliates of the registrant was approximately $599,169,357 as of June 30, 2009, based upon the closing sale price on The NASDAQ Global Market reported on June 30, 2009. Excludes an aggregate of 6,622,844 shares of the registrant’s common stock held by officers, directors and affiliated stockholders. For purposes of determining whether a stockholder was an affiliate of the registrant at June 30, 2009, the registrant assumed that a stockholder was an affiliate of the registrant at June 30, 2009 if such stockholder (i) beneficially owned 10% or more of the registrant’s common stock, as determined based on public filings, and/or (ii) was an executive officer or director or was affiliated with an executive officer or director of the registrant at June 30, 2009. Exclusion of such shares should not be construed to indicate that any such person possesses the power, direct or indirect, to direct or cause the direction of the management or policies of the registrant or that such person is controlled by or under common control with the registrant.

There were 34,004,318 shares of Registrant’s Common Stock, par value $0.01 per share, issued and outstanding as of March 8, 2010.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s definitive Proxy Statement for the 2010 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission pursuant to Regulation 14A not later than 120 days after the end of the fiscal year covered by this Form 10-K are incorporated by reference in Part III, Items 10-14 of this Form 10-K.

EXPLANATORY NOTE

We are filing this Amendment No. 1 to Annual Report on Form 10-K/A (this “Amendment”) to amend our Annual Report on Form 10-K for the fiscal year ended December 31, 2009, as filed with the Securities and Exchange Commission (the “SEC”) on March 15, 2010 (the “Form 10-K”). This Amendment is being filed solely to file Exhibit 10.15 to the Form 10-K (certain portions of which are omitted pursuant to a confidential treatment request filed with the SEC). In addition, as required by Rule 12b-15 under the Securities Exchange Act of 1934, as amended, new certifications by our principal executive officer and principal financial officer are filed as exhibits hereto.

No attempt has been made in this Amendment to modify or update the other disclosures presented in the Form 10-K including the change in our filing status to a large accelerated filer. This Amendment does not reflect events occurring after the filing of the Form 10-K (i.e., occurring after March 15, 2010) or modify or update those disclosures that may be affected by subsequent events. Such subsequent matters are addressed in subsequent reports filed by the registrant with the SEC. Accordingly, this Amendment should be read in conjunction with the Form 10-K and the registrant’s other filings with the Securities and Exchange Commission.

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the Registrant has duly caused this Amendment No. 1 to Annual Report on Form 10-K/A to be signed on its behalf by the undersigned, thereunto duly authorized

EXHIBIT INDEX