UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

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

January 20, 2009

Date of Report (Date of earliest event reported)

SONUS NETWORKS, INC.

(Exact Name of Registrant as Specified in its Charter)

7 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):

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

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

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

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

The information in this Current Report on Form 8-K shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On January 20, 2009, the Registrant’s Board of Directors (the “Board”) appointed John Schofield as a director to fill a vacancy on its Board.  Mr. Schofield will serve until the 2011 Annual Meeting of Stockholders or his successor is duly appointed and qualified.

Since 2001, Mr. Schofield has served as the Chairman of the Board of Directors of Integrated Device Technology, Inc.  From March 1999 to January 2005, Mr. Schofield was Chairman, President, Chief Executive Officer and Director of Advanced Fibre Communications, Inc.  In 2004, Mr. Schofield was a member of the Board of Directors of Telecommunications Industry Association.  Mr. Schofield was recommended to the Board by the Nominating Committee of the Board in accordance with the provisions of the Nominating Committee Charter.

There are no arrangements or understandings between Mr. Schofield and any other person pursuant to which Mr. Schofield was elected as a director.  Mr. Schofield has been appointed to serve on the Audit Committee of the Board.  There are no transactions in which Mr. Schofield has an interest requiring disclosure under Item 404(a) of Regulation S-K.

Mr. Schofield will be granted a stock option, pursuant to the Registrant’s 2007 Stock Incentive Plan, to purchase 50,000 shares of the Registrant’s common stock with an exercise price equal to the closing share price of the Registrant’s common stock on the date of grant, February 15, 2009.  Such option will vest over a four-year period so long as Mr. Schofield remains a member of the Board.

A copy of the press release announcing Mr. Schofield’s election is attached as Exhibit 99.1 hereto.

Item 9.01. Financial Statements and Exhibits.

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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.

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Exhibit Index

4

Exhibit 99.1

FOR IMMEDIATE RELEASE

SONUS NETWORKS APPOINTS JOHN SCHOFIELD TO BOARD OF DIRECTORS

Former Chairman, President and Chief Executive Officer Of Advanced Fibre
 Communications Joins Leading Provider Of IP-Voice Technology

Westford, MA, January, 20, 2009 - Sonus Networks (Nasdaq: SONS), a market leader in IP communications infrastructure, today announced that John Schofield has been appointed to its Board of Directors and will serve as a member of the Sonus Audit Committee.  Mr. Schofield brings to Sonus extensive telecommunications experience from a career spanning thirty years and three continents and over ten years of experience as an active board member.

Most recently, Mr. Schofield served as the chairman, president and chief executive officer at Advanced Fibre Communications (AFC) from 1999 until the completion of its merger with Tellabs, Inc. in 2005.  During that time he successfully rebuilt the management team, sustained revenue growth and oversaw the development of end-to-end solutions to deliver voice, internet and video on a single network.  Prior to joining AFC, Mr. Schofield held multiple senior positions in sales, marketing, distribution and general management at Memorex Telex Corporation, Telex Communications, Inc., ADC Telecommunications and Raytheon Company.

“John’s broad experience as a senior executive within the telecommunications industry makes him a valuable addition to our Board,” commented Howard Janzen,

chairman of the board at Sonus Networks.  “John shares the Sonus vision for bringing innovative technology to customers around the world and the commitment to build long-term shareholder value. We look forward to working with him.”

Mr. Schofield also currently serves as chairman of the board at Integrated Device Technology, Inc (IDT) (Nasdaq: IDTI), a specialist in semiconductor solutions.  Previously, he held board positions with the United Way of Sonoma/Lake/Mendocino Counties, the School of Business and Economics at Sonoma State University, Turin Networks, Redfern Broadband Networks and served on the Council on Diversity for the Telecommunications Industry Association.

Mr. Schofield holds a bachelor of science degree in electrical engineering from NSW Institute of Technology in Sydney, Australia.

This appointment fills the open seat left by Hassan Ahmed, who announced his retirement from the Sonus Board of Directors in December 2008.

About Sonus Networks

Sonus Networks, Inc. is a market leader in IP communications infrastructure for wireline and wireless service providers.  With its comprehensive IP Multimedia Subsystem (IMS) solution, Sonus addresses the full range of carrier applications, including residential and business voice services, wireless voice and multimedia, trunking and tandem switching, carrier interconnection and enhanced services.  Sonus’ voice infrastructure solutions are deployed in service provider networks worldwide.  Founded in 1997, Sonus is headquartered in Westford, Massachusetts.  Additional information on Sonus is available at http://www.sonusnet.com.

This release may contain forward-looking statements regarding future events that involve risks and uncertainties. Readers are cautioned that these forward-looking statements are only predictions and may differ materially from actual future events or results.  Readers are referred to Item 1A “Risk Factors” of our Annual Report on Form 10-K for the year ended December 31, 2007 and all subsequent Quarterly Reports on Form 10-Q, which identify important risk factors that could cause actual results to differ from those contained in the forward-looking statements.  Risk factors include among others: the Company’s ability to align its cost structure with market conditions, the impact of material weaknesses in our disclosure controls and procedures and our internal control over financial reporting on our ability to report our financial results timely and accurately; the unpredictability of our quarterly financial results; risks and uncertainties associated with the Company’s restatement of its historical stock option granting practices and accounting including regulatory actions; actions that may be taken by significant shareholders; risks associated with our international expansion; and the impact the current global financial market conditions may have on the telecommunications industry.  Any forward-looking statements represent Sonus’ views only as of today and should not be relied upon as representing Sonus’ views as of any subsequent date.  While Sonus may elect to update forward-looking statements at some point, Sonus specifically disclaims any obligation to do so, except as required by law.

Sonus is a registered trademark of Sonus Networks, Inc. All other company and product names may be trademarks of the respective companies with which they are associated.