UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q/A

(Amendment No. 1)

QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF

THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended June 30, 2012

Commission file number: 1-5794

Masco Corporation

(Exact name of Registrant as Specified in its Charter)

(313) 274-7400

(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.

x  Yes    ¨  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 (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).

x  Yes    ¨  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    x  No

Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest practicable date.

MASCO CORPORATION

EXPLANATORY NOTE

This Amendment No. 1 (the “Amendment”) to Masco Corporation’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2012 (the “Form 10-Q”), filed with the Securities and Exchange Commission on July 31, 2012 (the “Filing Date”), is filed solely to revise our disclosure in Part II, Item 1, Legal Proceedings. No other changes to our Form 10-Q are made in this Amendment. This Amendment speaks as of the Filing Date, does not reflect events that may have occurred subsequent to the Filing Date, and, other than as set forth below, does not modify or update the disclosures made in the Form 10-Q. Accordingly, this Amendment should be read in conjunction with the Form 10-Q.

PART II. OTHER INFORMATION

Information regarding legal proceedings involving us is set forth in Note N to our condensed consolidated financial statements included in Part I, Item 1 of this Report and is incorporated herein by reference.

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MASCO CORPORATION

PART II. OTHER INFORMATION, concluded

SIGNATURE

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 thereunto duly authorized.

August 1, 2012

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MASCO CORPORATION

EXHIBIT INDEX

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