UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K/A

(Amendment No. 1)

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

August 24, 2011

Date of Report (Date of earliest event reported)

SONUS NETWORKS, INC.

(Exact Name of Registrant as Specified in its Charter)

4 TECHNOLOGY PARK DRIVE, WESTFORD, MASSACHUSETTS 01886

(Address of Principal Executive Offices) (Zip Code)

(978) 614-8100

(Registrant’s telephone number, including area code)

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 (see General Instruction A.2. below):

o            Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o            Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o            Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o            Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Explanatory Note

Sonus Networks, Inc. (the “Company”) is filing this amendment to its Current Report on Form 8-K, dated August 24, 2011 (the “Original Filing”), in order to correct the terms of compensation of Maurice Castonguay, Senior Vice President and Chief Financial Officer of the Company.

(c)  The terms of the August 24, 2011 employment letter between the Company and Maurice Castonguay (the “Castonguay Employment Letter”) have been corrected as of October 25, 2011 to reflect 2012 as the Performance Period for the Performance Shares.

Paragraph 3(d)(ii)(A) of the Castonguay Employment Letter filed as Exhibit 10.1 of the Original Filing shall now read, in its entirety

“the Company must achieve certain performance metrics between January 1, 2012 and December 31, 2012 (the “Performance Period”); and”

All other terms of the Castonguay Employment Letter in Exhibit 10.1 of the Original Filing remain unchanged.

The foregoing summary is qualified in its entirety by reference to the Amendment to Employment Agreement between Sonus Networks, Inc. and Maurice Castonguay, dated October 25, 2011, a copy of which is attached as Exhibit 10.1 to this Current Report on Form 8-K/A and incorporated herein by reference.

(d)  Exhibits

10.1 Amendment to Employment Agreement between Sonus Networks, Inc. and Maurice Castonguay, dated October 25, 2011

2

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.

3

Exhibit 10.1

October 25, 2011

Mr. Maurice Castonguay

<By Electronic Delivery>

Dear Moe:

This letter confirms a correction to your employment letter dated August 24, 2011 (your “Employment Letter”).  Terms not defined herein shall have the same meanings given to them in the Employment Letter.

Paragraph 3(d)(ii)(A) of the Employment Letter shall be deleted and replaced in its entirety with the following:

“the Company must achieve certain performance metrics between January 1, 2012 and December 31, 2012 (the “Performance Period”); and”

Except as expressly modified hereby, the terms of the Employment Letter shall remain in full force and effect.

Please confirm your acceptance by signing below.