UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Amendment No. 1

To

FORM 10-Q

x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended: March 31, 2015

OR

¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from ______________to ______________

Commission File Number: 000-53166

MUSCLEPHARM CORPORATION

(Exact name of registrant as specified in its charter)

4721 Ironton Street, Building A

Denver, Colorado 80239

(Address of principal executive offices and zip code)

(303) 396-6100

(Registrant’s telephone number, including area code)

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 past 12 months, and (2) has been subject to such filing requirements for the past 90 days. Yes x 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. Yes x No ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or a non-accelerated filer, or a smaller reporting company. See the 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 Exchange Act). Yes ¨ No x

Number of shares of the registrant’s common stock outstanding at May 1, 2015:13,492,191, excluding 875,621 common shares held in treasury.

EXPLANATORY NOTE

The following is Amendment No. 1 to the Quarterly Report on Form 10-Q for the three months ended March 31, 2015 (the “Form 10-Q”) of MusclePharm Corporation. This Amendment No. 1 is being filed to solely to refile Exhibit 10.4, the Option Agreement by and between MusclePharm Corporation and F.H.G Corporation, effective March 2, 2015 (the “Agreement”) to the Form 10-Q to include certain portions of such exhibit which had been omitted from such exhibit when filed with the Form 10-Q pursuant to a request for confidential treatment filed with the SEC (the “CTR”).

This Form 10-Q/A should be read in conjunction with the Form 10-Q, which continues to speak as of the date of the Form 10-Q. Except as specifically noted above, this Form 10-Q/A does not modify or update disclosures in the original Form 10-Q. Accordingly, this Form 10-Q/A does not reflect events occurring after the filing of the Form 10-Q or modify or update any related or other disclosures.

PART II. OTHER INFORMATION

Item 6. 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, thereunto duly authorized.