UNITED STATES

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): May 11, 2015 (May 6, 2015)

HCA HOLDINGS, INC.

(Exact Name of Registrant as Specified in Charter)

Registrant’s telephone number, including area code: (615) 344-9551

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Item 1.01 Entry into a Material Definitive Agreement.

Underwriting Agreement

On May 6, 2015, HCA Inc. (the “Issuer”), a wholly owned subsidiary of HCA Holdings, Inc. (the “Parent Guarantor”), entered into an Underwriting Agreement (the “Underwriting Agreement”) with Citigroup Global Markets Inc., Barclays Capital Inc., Credit Suisse Securities (USA) LLC, Deutsche Bank Securities Inc., Goldman, Sachs & Co., J.P. Morgan Securities LLC, Merrill Lynch, Pierce, Fenner & Smith Incorporated, Morgan Stanley & Co. LLC, RBC Capital Markets, LLC, SunTrust Robinson Humphrey, Inc., UBS Securities LLC and Wells Fargo Securities, LLC as representatives of the several underwriters named therein, for the issuance and sale by the Issuer of $1,600,000,000 aggregate principal amount of its 5.375% Senior Notes due 2025 (the “Notes”), guaranteed on a senior unsecured basis by the Parent Guarantor, pursuant to the Issuer’s and the Parent Guarantor’s shelf registration statement on Form S-3, filed on January 13, 2015 (File No. 333-201463), as supplemented by the prospectus supplement dated May 6, 2015, previously filed with the Securities and Exchange Commission under the Securities Act of 1933, as amended.

The Notes will be issued under the indenture (as amended, restated, modified or supplemented from time to time, the “Indenture”) governing the $1.0 billion aggregate principal amount of the Issuer’s 5.375% Senior Notes due 2025 that were issued on January 16, 2015 (the “Existing Notes”) and will have identical terms with the Existing Notes, other than their issue date and public offering price. The Notes and the Existing Notes will be treated as a single series for all purposes under the Indenture, including notices, consents, waivers, amendments, redemptions and any other action permitted under the Indenture. The Notes will have the same CUSIP and ISIN numbers as, and will vote together and will be fungible with, the Existing Notes immediately upon issuance.

The description of the Underwriting Agreement is qualified in its entirety by the terms of such agreement, which is incorporated herein by reference and attached to this report as Exhibit 1.1.

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

The information provided in Item 1.01 of this report is incorporated by reference into this Item 2.03.

Item 9.01 Financial Statements and Exhibits.

SIGNATURES

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.

Date: May 11, 2015

INDEX TO EXHIBITS