As filed with the Securities and Exchange Commission on July 21, 2015

Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Blue Buffalo Pet Products, Inc.

(Exact name of registrant as specified in its charter)

11 River Road

Wilton, CT 06897

(203) 762-9751

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Michael Nathenson

Chief Financial Officer

Blue Buffalo Pet Products, Inc.

Wilton, CT 06897

(203) 762-9751

(Name, address, including zip code, and telephone number, including area code, of agent for service)

With copies to:

Approximate date of commencement of the proposed sale of the securities to the public: As soon as practicable after the Registration Statement is declared effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box:  ¨

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  x Registration No. 333-204847

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

CALCULATION OF REGISTRATION FEE

This Registration Statement shall become effective upon filing with the Securities and Exchange Commission in accordance with Rule 462(b) promulgated under the Securities Act.

EXPLANATORY NOTE AND INCORPORATION OF

CERTAIN INFORMATION BY REFERENCE

This Registration Statement on Form S-1 is being filed with the Securities and Exchange Commission (the “Commission”) pursuant to Rule 462(b) under the Securities Act of 1933, as amended, by Blue Buffalo Pet Products, Inc. (the “Registrant”). This Registration Statement incorporates by reference the contents of, including all exhibits to, the Registrant’s Registration Statement on Form S-1 (File No. 333-204847), as amended, which was declared effective by the Commission on July 21, 2015.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant, has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in Wilton, State of Connecticut, on the 21st day of July, 2015.

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement and power of attorney have been signed by the following persons in the capacities indicated on the 21st day of July, 2015.