SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): March 27, 2015

USMD Holdings, Inc.

(Exact name of registrant as specified in its charter)

6333 North State Highway 161, Suite 200

Irving, Texas 75038

(Address of principal executive offices)

Registrant’s telephone number, including area code: (214) 493-4000

Check the appropriate box if the Form 8-K filing is intended to simultaneously satisfy the reporting obligation of the registrant under any of the following provisions:

On March 27, 2015, the Company issued $3,500,000 in convertible subordinated notes due 2020 (the “Notes”) to certain investors in a private unregistered offering. The information contained in Item 2.03 below is incorporated into this Item 1.01.

Also on March 27, 2015, board of directors of the Company approved the Company’s entry into Amendment No. 7 to Credit Agreement dated as of March 13, 2015 (the “Amendment”) with Southwest Bank, as administrative agent for the lenders, to amend that certain Credit Agreement dated August 31, 2012 (as previously amended, the “Credit Agreement”) by and among the Company, certain other borrowers and the lenders. The amendment modified the limitation on indebtedness contained in the Credit Agreement to allow the indebtedness evidenced by the Notes. The foregoing description of the Amendment is qualified in its entirety by reference to the text of the Amendment, which is attached hereto as Exhibit 10.1 and incorporated by reference herein.

Item 2.03 Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

On March 27, 2015, the Company issued convertible subordinated notes due 2020 in the principal amount of $3,500,000. The Notes mature on September 1, 2020 and bear interest at a rate of 7.75% per annum. Interest will be due and payable monthly on the last day of each month commencing on April 30, 2015. The Company may prepay the Notes, in whole or in part, at any time after March 13, 2016. In order to prepay the Notes, the Company must provide 60 days’ prior written notice of its intent to prepay the Notes to the holders of the Notes. Each noteholder will have the right at any time after March 13, 2016, prior to the payment in full of the Note, to convert all or any part of the unpaid principal balance of the Note into shares of common stock of the Company at the rate of one share of common stock for each $12.02 of principal. The conversion rate will be appropriately adjusted for stock splits, mergers or other fundamental corporate transactions. The indebtedness represented by the Notes is expressly subordinate to and junior and subject in right of payment to the prior payment in full in cash of all senior indebtedness of the Company, which includes its indebtedness in connection with the Credit Agreement. The foregoing description of the Notes is qualified in its entirety by reference to the form of the Notes, which is attached hereto as Exhibit 4.1 and incorporated by reference herein.

Because the Notes are convertible at any time after March 13, 2016 into shares of the Company’ common stock, the issuance of the Notes may be deemed to constitute a sale of equity securities of the Company. Upon issuance, the shares of common stock into which the Notes are convertible will not be registered under the Securities Act of 1933, as amended (the “Securities Act”) in reliance on the exemption provided by Regulation S promulgated under the Securities Act. The Company is relying upon the safe harbor provision of Rule 903 of Regulation S of the Securities Act which permits offers or sales of securities by the Company outside of the United States that are not made to “U.S. persons” or for the account or benefit of a “U.S. person”, as that term is defined in Rule 902 of Regulation S.

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 hereunto duly authorized.