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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

(Amendment No. 1)

(Mark One)

or

Commission file number 001-32559

Medical Properties Trust, Inc.

MPT Operating Partnership, L.P.

(Exact Name of Registrant as Specified in Its Charter)

(205) 969-3755

(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  þ    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  þ

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  þ    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its 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).    Yes  þ    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 the registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment of this Form 10-K.  ¨

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. (Check one):

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

As of June 30, 2011, the aggregate market value of the 111,712,079 shares of common stock, par value $0.001 per share (“Common Stock”), held by non-affiliates of the registrant was $1,284,688,909 based upon the last reported sale price of $11.50 on the New York Stock Exchange. For purposes of the foregoing calculation only, all directors and executive officers of the registrant have been deemed affiliates.

As of February 22, 2012, 135,275,389 shares of Medical Properties Trust, Inc. Common Stock were outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s definitive Proxy Statement for the Annual Meeting of Stockholders to be held on May 17, 2012 are incorporated by reference into Items 10 through 14 of Part III, of this Annual Report on Form 10-K.

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MEDICAL PROPERTIES TRUST, INC.

MPT OPERATNIG PARTNERSHIP, L.P.

AMENDMENT NO. 1 TO ANNUAL REPORT ON FORM 10-K

FOR THE FISCAL YEAR ENDED DECEMBER 31, 2011

This Amendment No. 1 to the Annual Report on Form 10-K for the fiscal year ended December 31, 2011 of Medical Properties Trust, Inc. and MPT Operating Partnership, L.P. is filed for the sole purpose of adding the consolidated financial statements of Prime Healthcare Services, Inc. and Subsidiaries (“Prime”) as Exhibit 99.1. At December 31, 2011, our properties leased to Prime were significant to our total assets. Since these properties are leased to Prime under long-term, triple-net leases that transfer substantially all operating costs to Prime, financial information about Prime may be relevant to investors. The audited financial statements of Prime for the years ended December 31, 2011 and 2010 are attached to this report as Exhibit 99.1. Refer to our 2010 Form 10-K/A filed on April 12, 2011 for the audited financial statements of Prime for the years ended December 31, 2010 and 2009. These financial statements were provided to us by Prime and Medical Properties Trust, Inc. did not participate in their preparation or review. Accordingly, Item 15 of Part IV has also been amended to reflect the filing of these exhibits.

Other than as expressly set forth above, this Amendment does not, and does not purport to, update or restate the information in any other Item of the originally filed annual report.

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PART IV

(a) Financial Statements and Financial Statement Schedules

The financial statements and financial statement schedules were previously filed with the Annual Report on Form 10-K for the fiscal year ended December 31, 2011, filed on February 29, 2012.

(b) Exhibits

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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.

Date: May 10, 2012

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INDEX TO EXHIBITS