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 6, 2015

QTS Realty Trust, Inc.

(Exact name of registrant as specified in its charter)

(913) 814-9988

Registrant’s telephone number, including area code:

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:

Item 7.01. Regulation FD Disclosure.

QTS Realty Trust, Inc. (the “Company”), through a subsidiary, entered into a stock purchase agreement with Carpathia Holdings, LLC and Carpathia Acquisition, Inc. dated May 6, 2015 (the “Stock Purchase Agreement”) pursuant to which it will acquire the business of Carpathia Hosting, Inc. for approximately $326 million. The Company issued a press release on May 6, 2015 announcing the proposed transaction. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

The slides used in connection with the analyst and investor presentation are attached hereto as Exhibit 99.2 and are incorporated herein by reference.

The information required to be reported on Form 8-K with respect to the Stock Purchase Agreement will be filed in a separate Current Report on Form 8-K.

Cautionary Statement Regarding Forward-Looking Statements

Some of the statements contained in this Current Report on Form 8-K constitute forward-looking statements within the meaning of the federal securities laws. These forward-looking statements include, among other things, information about the Company’s properties and its redevelopment pipeline. Forward-looking statements relate to expectations, beliefs, projections, future plans and strategies, anticipated events or trends and similar expressions concerning matters that are not historical facts. In some cases, you can identify forward-looking statements by the use of forward-looking terminology such as “may,” “will,” “should,” “expects,” “intends,” “plans,” “anticipates,” “believes,” “pro forma,” “estimates,” “predicts,” or “potential” or the negative of these words and phrases or similar words or phrases which are predictions of or indicate future events or trends and which do not relate solely to historical matters. You can also identify forward-looking statements by discussions of strategy, plans or intentions.

The forward-looking statements contained in this Current Report on Form 8-K reflect the Company’s current views about future events and are subject to numerous known and unknown risks, uncertainties, assumptions and changes in circumstances that may cause actual results to differ significantly from those expressed in any forward-looking statement. The Company does not guarantee that the transaction and events described will happen as described (or that they will happen at all). The following factors, among others, could cause actual results and future events to differ materially from those set forth or contemplated in the forward-looking statements: adverse economic or real estate developments in the Company’s markets or the technology industry; national and local economic conditions; difficulties in identifying properties to acquire and completing acquisitions; the Company’s failure to successfully develop, redevelop and operate acquired properties; significant increases in construction and development costs; the increasingly competitive environment in which the Company operates; defaults on or non-renewal of leases by customers; increased interest rates and operating costs, including increased energy costs; financing risks, including the Company’s failure to obtain necessary outside financing; decreased rental rates or increased vacancy rates; dependence on third parties to provide Internet, telecommunications and network connectivity to the Company’s data centers; the Company’s failure to qualify and maintain its qualification as a real estate investment trust; environmental uncertainties and risks related to natural disasters; financial market fluctuations; and changes in real estate and zoning laws and increases in real property tax rates.

While forward-looking statements reflect the Company’s good faith beliefs, they are not guarantees of future performance. The Company disclaims any obligation to publicly update or revise any forward-looking statement to reflect changes in underlying assumptions or factors, of new information, data or methods, future events or other changes. For a further discussion of these and other factors that could cause the Company’s future results to differ materially from any forward-looking statements, see the section entitled “Risk Factors” in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 and other documents that it files from time to time with the Securities and Exchange Commission.

The information included in this Current Report on Form 8-K under this Item 7.01 shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any filing made by the Company under the Exchange Act or the Securities Act of 1933, as amended, except as shall be expressly set forth by specific reference in such a filing.

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.

May 6, 2015

EXHIBIT INDEX