David A. Westenberg



David Westenberg is a partner in the Corporate Practice Group and the Capital Markets Group. He joined the firm in 1983.


Mr. Westenberg has focused on the software, Internet and information technology industries for more than twenty years, guiding numerous startup clients from formation through venture financing and on to successful acquisitions or IPOs. As outside corporate counsel to many public and private companies, Mr. Westenberg advises clients on a wide variety of corporate, securities, disclosure and governance matters. His transactional experience includes more than 50 IPOs and other capital markets transactions, as well as a large number of venture capital financings and M&A transactions. He is the author of Initial Public Offerings: A Practical Guide to Going Public  (Practising Law Institute), a comprehensive yet practical guide to the IPO process that has been hailed for its unprecedented breadth, depth and ease of use and was dubbed the "bible of the IPO market" by The New York Times (The Deal Professor, January 19, 2010).

Recent Highlights

  • $90 million IPO of Casa Systems
  • Blue Apron's $300 million IPO
  • Acacia Communications' $119 million IPO and $517 million follow-on public offering
  • Sale of Gilt Groupe to Hudson's Bay Company for $250 million
  • HubSpot's $144 million IPO and $167 million follow-on public offering (underwriters' counsel)  
  • Imprivata's IPO raising $86 million (underwriters' counsel) 
  • Endurance International Group's IPO raising $252 million and follow-on public offerings raising a total of $479 million 
  • Late-stage and crossover financings for various clients, including Blue Apron ($135 million) and Gilt Groupe ($50 million) 
  • SS&C Technologies Holdings' IPO and follow-on public offerings raising an aggregate of more than $1.4 billion 
  • Bottomline Technologies' follow-on public offerings of common stock and convertible senior notes raising a total of more than $250 million
  • Kiva Systems' acquisition by for $775 million
  • Brightcove's IPO raising $63 million (underwriters' counsel)
  • Tangoe's $101 million IPO and $170 million follow-on public offering
  • Accretive Health's $138 million IPO and $175 million follow-on public offering
  • Netezza's acquisition by IBM for $1.7 billion
  • "Dual track" IPO/sale for EqualLogic, resulting in $1.4 billion acquisition by Dell—the largest cash purchase price in history for a private VC-backed company
  • "Dual track" IPO/sale for McLeodUSA, resulting in $557 million acquisition by PAETEC Holding
  • Sale of MapInfo to Pitney Bowes for $472 million
  • Cynosure's IPO raising $86 million
  • Sale of MatrixOne to Dassault Systèmes for $408 million
  • Avid's acquisition of Pinnacle Systems for $462 million
  • Prodigy's IPO (then the largest Internet company IPO in history) and its $1.6 billion strategic transaction with SBC Communications
  • Venture capital financings for various clients 

Honors and Awards

  • Recognized as a leader for Corporate/M&A: Capital Markets in the 2013-2017 editions of Chambers USA: America's Leading Lawyers for Business
  • Recommended in the 2016 and 2017 editions of The Legal 500 United States for finance: capital markets: equity offerings: advice to managers
  • Mr. Westenberg's book, Initial Public Offerings: A Practical Guide to Going Public, received the 2013 "Outstanding Authoritative Book by a Partner in a Law Firm" award, given annually by the Burton Foundation to one book that represents "an important contribution to the legal profession" and "is comprehensive in scope, informative, incisive, and is an important reference and informational tool" 
  • Named by Best Lawyers in America as Boston's Technology Law Lawyer of the Year for 2018 and 2012 and Boston's Information Technology Law Lawyer of the Year for 2015, and is consistently ranked as one of the Best Lawyers in America in the areas of corporate, information technology, mergers & acquisitions, venture capital and technology law
  • WilmerHale's IPO, Venture Capital and M&A Reports, co-authored by Mr. Westenberg, received a Best Law Firm Publication Award given by the Burton Foundation in 2006 for excellence in legal writing 
  • Named in Boston Magazine as a "New England Super Lawyer" (formerly "Massachusetts Super Lawyer") each year since 2004 
  • Selected by American Lawyer magazine as "Dealmaker of the Year" for equities (2001)
  • Named an "All Star for Law & Technology" by Mass High Tech for fostering the development of New England technology companies (1999)

Publications & News


December 21, 2017

WilmerHale Represents Casa Systems in Initial Public Offering

On December 19, 2017, Casa Systems, Inc., a provider of software-centric solutions for next-generation distributed and virtualized architectures in cable operator, fixed telecom and wireless networks, closed its initial public offering.

August 16, 2017

WilmerHale Lawyers Named Among the 2018 Best Lawyers in America®, Nine Recognized as Lawyers of the Year

Best Lawyers in America®—the oldest and most respected peer-review publication in the legal industry—recognizes 107 WilmerHale lawyers and names nine partners as Lawyers of the Year in its 24th edition.

July 5, 2017

WilmerHale Represents Blue Apron Holdings, Inc. in IPO

Blue Apron's mission is to make incredible home cooking accessible to everyone. Launched in 2012, Blue Apron has grown to $795 million in annual revenue to become the leading US meal plan delivery company.

June 14, 2017

Special Considerations in California M&A Deals

Deal Lawyers published this article by David Westenberg and Joe Wyatt in its June-August 2017 issue.

June 9, 2017

The Legal 500 United States 2017 Recognizes 125 WilmerHale Lawyers Across 28 Practice Areas

The Legal 500 United States has released its 2017 rankings, recommending 125 WilmerHale lawyers—including 12 who are named to its elite “Leading Lawyers” list and two on its “Next Generation Lawyers” list—and 28 practice areas in its 11th edition.

May 26, 2017

WilmerHale Lawyers and Practices Recognized in 2017 Edition of Chambers USA

Chambers and Partners announced its rankings for the 2017 edition of Chambers USA: America's Leading Lawyers for Business, with WilmerHale listed among the nation's best in 50 practice area categories. Chambers also ranked 86 WilmerHale lawyers as leaders in their respective fields.

May 5, 2017

WilmerHale Reps Tangoe in Acquisition by Marlin Equity Partners

WilmerHale client Tangoe, Inc., a global leader in telecom expense management solutions, and Marlin Equity Partners, a global investment firm, entered into a definitive agreement for Marlin to acquire all outstanding shares of Tangoe not already owned by Marlin for $6.50 per share in cash.

April 28, 2017

2017 IPO Report

Our 2017 IPO Report offers a detailed analysis of, and outlook for, the IPO market, plus useful IPO market metrics. We look at rates of adoption of JOBS Act relief by emerging growth companies, the potential impact of the new presidential administration on policy and direction at the US Securities and Exchange Commission and much more.

April 28, 2017

2017 M&A Report

Our 2017 M&A Report provides a detailed global M&A market review and outlook. Other highlights include takeover defenses for public companies; key lessons for buyers and sellers considering earnouts; recent developments in merger control regulation; common interest privilege protection among deal parties; special considerations in California M&A deals; acquisition financial statement requirements for IPO companies; a comparison of deal terms in public and private acquisitions; and key terms and issues in sales of VC-backed companies.

April 28, 2017

2017 Venture Capital Report

The 2017 Venture Capital Report offers an in-depth US venture capital market review and outlook, including industry and regional breakdowns, as well as a look at the following issues: steps startups should take now if they plan to secure a Series A round in 2017; common structures for management carve-out plans; best practices for private companies setting option exercise prices; the benefits of investing in qualified small business stock; and trends in venture capital financing terms, convertible debt terms and VC-backed company M&A deal terms.


The Road to IPO: Legal and Regulatory Insights into Going Public blog focuses on IPOs, including legal and regulatory developments affecting the IPO market, analysis of market practices, and information of interest to all companies planning or hoping to go public. Blog host David Westenberg, a partner in the firm’s capital markets group, is one of the country’s foremost authorities on IPOs. He writes and is quoted frequently on the IPO market, and is the author of the acclaimed book, Initial Public Offerings: A Practical Guide to Going Public.

Speaking Engagements

December 7, 2017

WilmerHale and RSM Event: State of the Technology Market

Charlestown, Massachusetts

November 28, 2017

Harvard Law School: Securities Regulation Class

Cambridge, Massachusetts

March 2, 2017

The IPO Playbook: An Insider's Guide to Going and Being Public

Waltham, Massachusetts

September 22, 2016

Ready, Set...IPO

Waltham, Massachusetts

April 8, 2015

Ready, Set ... IPO

Waltham, Massachusetts

March 25, 2014

Going Public: An Inside Look at IPO Preparation

Waltham, Massachusetts

May 21, 2013

Ready, Set ... IPO

Waltham, Massachusetts

October 16, 2012

Going Public: An Inside Look at IPO Preparation

Waltham, Massachusetts

June 4, 2012

IPO Market on the Upswing: The JOBS Act and Other Recent Developments


February 7, 2012

Ready, Set ... IPO

Waltham, Massachusetts

Professional Activities

Mr. Westenberg is active in various technology councils and is a former co-chair of the Corporate Law Committee of the Boston Bar Association.

Mr. Westenberg writes frequently on the IPO and venture capital markets, and has been quoted or featured in The American Lawyer, Boston Business Journal, The Boston Globe, Boston Magazine,,, Investor’s Business Daily and The Wall Street Journal.


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JD, Harvard Law School, 1983

SB, Massachusetts Institute of Technology, 1979

Bar Admissions


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