UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

Amendment No. 1

For the fiscal year ended December 31, 2012

OR

Commission file number 001-34456

COLONY FINANCIAL, INC.

(Exact Name of Registrant as Specified in Its Charter)

(310) 282-8820

(Registrant’s Telephone Number, Including Area Code)

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 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 Website, 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 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.  ¨

Indicate by check mark whether the registrant is a large accelerated filed, 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 voting and non-voting common equity held by non-affiliates of the registrant was approximately $559.9 million as of the last business day of the registrant’s most recently completed second fiscal quarter based upon the price at which the common shares were last sold on that day.

As of March 6, 2013, 64,591,623 shares of the Registrant’s common stock, par value $0.01 per share, were outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the Company’s Proxy Statement with respect to its 2013 Annual Meeting of Stockholders to be filed not later than 120 days after the end of the Company’s fiscal year are incorporated by reference into Part III of this Form 10-K.

EXPLANATORY NOTE

This Form 10-K/A is being filed as Amendment No. 1 to the Form 10-K of Colony Financial, Inc. filed with the U.S. Securities and Exchange Commission on March 11, 2013 (the “Original Form 10-K”) for the purpose of amending the Consent of Independent Registered Certified Public Accounting Firm to correct a typographical error with respect to the date of such consent. There are no other changes to the consent or to the Original Form 10-K.

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

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