UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 10-Q/A

(Amendment No. 1)

(Mark One)

For the quarterly period ended June 30, 2011

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, 36th floor

San Francisco, California 94105

(Address of principal executive offices) (Zip Code)

(415) 543-3470

(Registrant’s telephone number, including area code)

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  x    No  ¨

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 Exchange Act).    Yes  ¨    No  x

As of August 3, 2011, 34,907,994 shares of the registrant’s Common Stock, $0.01 par value per share, were outstanding.

EXPLANATORY NOTE

We are filing this Amendment No. 1 to Quarterly Report on Form 10-Q/A (this “Amendment”) to amend our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2011, as filed with the Securities and Exchange Commission (the “SEC”) on August 9, 2011 (the “Form 10-Q”). This Amendment is being filed solely to file Exhibit 10.2 to the Form 10-Q (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-Q, 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-Q (i.e., occurring after August 9, 2011) 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-Q 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 Quarterly Report on Form 10-Q/A to be signed on its behalf by the undersigned, thereunto duly authorized.

EXHIBIT INDEX