As filed with the Securities and Exchange Commission on April 19, 2011

No. 333-            

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Sagent Holding Co.*

(Exact name of registrant as specified in its charter)

c/o Sagent Pharmaceuticals, Inc.

1901 North Roselle Road, Suite 700

Schaumburg, Illinois 60195

(847) 908-1600

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

Michael Logerfo

Chief Legal Officer, Corporate Vice President and Secretary

c/o Sagent Pharmaceuticals, Inc.

1901 North Roselle Road, Suite 700

Schaumburg, Illinois 60195

(847) 908-1600

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

Copies of all communications, including communications sent to agent for service, should be sent to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after this Registration Statement becomes 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, 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.    þ File No. 333-170979

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.    ¨

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 the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act (Check one):

CALCULATION OF REGISTRATION FEE

THIS REGISTRATION STATEMENT SHALL BECOME EFFECTIVE UPON FILING WITH THE COMMISSION IN ACCORDANCE WITH RULE 462(b) UNDER THE SECURITIES ACT OF 1933, AS AMENDED.

EXPLANATORY NOTE AND INCORPORATION BY REFERENCE

This registration statement is being filed pursuant to Rule 462(b) (this “462(b) Registration Statement”) under the Securities Act of 1933, as amended. The contents of the Registration Statement on Form S-1 (File No. 333-170979), originally filed by the Registrant with the Securities and Exchange Commission (the “Commission”) on December 6, 2010, including the exhibits and power of attorney thereto, in the form which was declared effective by the Commission on April 19, 2011, is incorporated by reference.

This 462(b) Registration Statement is being filed for the purposes of registering additional shares of the Registrant’s common stock, par value $0.01 per share, which will be offered pursuant to this 462(b) Registration Statement.

Certification

The Registrant hereby certifies to the Commission that (i) it has instructed its bank to pay the filing fee set forth on the cover page of this Registration Statement by a wire transfer of such amount to the Commission’s account at US Bank as soon as practicable (but no later than the close of business as of April 20, 2011), (ii) it will not revoke such instructions, (iii) it has sufficient funds in the relevant account to cover the amount of such filing fee, and (iv) it will confirm receipt of such instructions by its bank during regular business hours no later than April 20, 2011.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant has duly caused this 462(b) Registration Statement on Form S-1 to be signed on its behalf by the undersigned, thereunto duly authorized, in the city of Schaumburg, state of Illinois, on April 19, 2011.

II-1

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, this 462(b) Registration Statement has been signed by the following persons in the capacities and on the date indicated.

II-2

EXHIBIT INDEX

All exhibits filed with or incorporated by reference in Registration Statement on Form S-1 (File No. 333-170979) are incorporated by reference into, and shall be deemed part of, this 462(b) Registration Statement, except the following, which are filed herewith: