UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

(Amendment No. 1)

For the fiscal year ended December 31, 2013

or

For the transition period from                      to                     

Commission file number 1-10994

VIRTUS INVESTMENT PARTNERS, INC.

(Exact name of registrant as specified in its charter)

100 Pearl St., Hartford, CT 06103

(Address of principal executive offices)

Registrant’s telephone number, including area code

(800) 248-7971

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

(Title of class)

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    x  Yes    ¨  No

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Exchange Act.    ¨  Yes    x  No

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.    x  Yes    ¨  No

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, 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).    x  Yes    ¨  No

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§229.405 of this chapter) is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to 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 definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

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

The aggregate market value of the registrant’s voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold (based on the closing share price as quoted on the NASDAQ Global Market) as of the last business day of the registrant’s most recently completed second fiscal quarter was $1,037,364,814. For purposes of this calculation, shares of common stock held or controlled by executive officers and directors of the registrant have been treated as shares held by affiliates.

There were 9,105,521 shares of the registrant’s common stock outstanding on February 13, 2014.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s Proxy Statement which will be filed with the SEC in connection with the 2014 Annual Meeting of Shareholders are incorporated by reference into Part III of this Form 10-K.

Explanatory Note

This Amendment No. 1 (“Amendment No. 1”) to the Annual Report on Form 10-K of Virtus Investment Partners, Inc. (together with its subsidiaries, the “Company,” “we,” “our,” “us” or “Virtus”) for the fiscal year ended December 31, 2013 as filed with the SEC on February 24, 2014 (the “2013 Annual Report”), is being filed to delete Item 12 of Part III and replace it in its entirety with the new Item 12 of Part III set forth in this Amendment No. 1.

PART III

The information set forth under the caption “Security Ownership by Certain Beneficial Owners and Management” in the Company’s Proxy Statement for the Company’s 2014 Annual Meeting of Shareholders is incorporated herein by reference.

The following table sets forth information as of December 31, 2013 with respect to compensation plans under which shares of our common stock may be issued:

EQUITY COMPENSATION PLAN INFORMATION

PART IV

The following exhibits are filed herewith:

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this amendment no. 1 to its annual report on Form 10-K to be signed on its behalf by the undersigned, thereunto duly authorized.

Dated: February 26, 2014