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): November 15, 2012

CYS Investments, Inc.

(Exact name of registrant as specified in its charter)

890 Winter Street, Suite 200

Waltham, Massachusetts 02451

(Address of principal executive offices)

Registrant’s telephone number, including area code: (617) 639-0440

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:

CYS Investments, Inc. (NYSE: CYS) (the “Company”) today announced that its Board of Directors has authorized the repurchase of shares of the Company’s common stock having an aggregate value of up to $250 million. As part of the stock repurchase program, shares may be purchased in open market transactions, including through block purchases, through privately negotiated transactions, or pursuant to any trading plan that may be adopted in accordance with Rule 10b5-1 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Open market repurchases will be made in accordance with Exchange Act Rule 10b-18, which sets certain restrictions on the method, timing, price and volume of open market stock repurchases. The timing, manner, price and amount of any repurchases will be determined by the Company in its discretion and will be subject to economic and market conditions, stock price, applicable legal requirements and other factors. The authorization does not obligate the Company to acquire any particular amount of common stock and the program may be suspended or discontinued at the Company’s discretion without prior notice.

Forward-Looking Statements Disclaimer

This Current Report on Form 8-K contains “forward-looking statements” made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995, including those relating to the planned stock repurchase program. Forward-looking statements typically are identified by use of the terms such as “believe,” “expect,” “anticipate,” “estimate,” “plan,” “continue,” “intend,” “should,” “may” or similar expressions. Forward-looking statements are based on the Company’s beliefs, assumptions and expectations of the Company’s future performance, taking into account all information currently available to the Company. The Company cannot assure you that actual results will not vary from the expectations contained in the forward-looking statements. All of the forward-looking statements are subject to numerous possible events, factors and conditions, many of which are beyond the control of the Company and not all of which are known to the Company, including, without limitation, market conditions and those described in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2011 and Quarterly Report on Form 10-Q for the quarter ended September 30, 2012, which have been filed with the Securities and Exchange Commission. All forward-looking statements speak only as of the date on which they are made. New risks and uncertainties arise over time, and it is not possible to predict those events or how they may affect us. Except as required by law, the Company is not obligated to, and does not intend to, update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.

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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.