Deidre J. Johnson


  • JD, Northeastern University School of Law, 1998
  • BS (English), summa cum laude, Boston College, 1995; Phi Beta Kappa; Golden Key National Honor Society


  • Massachusetts, 1998
  • French
  • Legal 500 (2016-2018, 2020)
  • The Best Lawyers in America (2016-2021)
    •  Lawyer of the Year, Antitrust Law (2021)
  • Chambers USA: America's Leading Lawyers for Business (2012-2020)
  • Massachusetts Super Lawyers Rising Star (2013-2014)

Deidre J. Johnson


Deidre Johnson focuses her practice on antitrust. As head of the firm's Premerger Notification practice, she counsels clients on their obligations under the Hart-Scott-Rodino Antitrust Improvements Act and foreign premerger regimes and has successfully guided numerous clients through the premerger process, responding to informal inquiries and second requests as necessary. She routinely represents buyers, shareholders and sellers in financial and strategic acquisitions of all types from leveraged buy-outs, stock acquisitions, joint venture formations, and public takeovers to licensing transactions and co-development/co-promotion agreements.

Deidre has prepared several hundred HSR filings and routinely coordinates merger clearances in multiple jurisdictions including the European Union and its member states, Brazil, Canada, China, Japan, Turkey, Russia, South Africa and South Korea, among others. Her clients include multi-national corporations, private equity, venture capital and hedge funds, mutual funds and investment advisors; she also counsels executive officers and directors in HSR Act compliance in connection with the grant and exercise of stock and stock options. She also advises clients with respect to permissible pre-clearance and pre-closing activities, including information exchanges.

Deidre frequently speaks on premerger matters, including most recently What Sponsors Need to Know About the Hart-Scott-Rodino (HSR) Rule Changes (July 2011) in conjunction with the Premerger Notification Office of the Federal Trade Commission.


  • $26 billion private equity-backed radio station buy-out involving market overlap and requiring merger clearance in eight countries
  • $2.4 billion food chain buy-out involving three-member consortium and filings in the U.S. and Germany
  • $11 billion technology company privatization by seven-member consortium
  • $471 million take-over bid for Japanese public company, requiring notification in the U.S., South Africa and the European Union
  • Formation of Korean biologics joint venture, requiring notification in the U.S., South Korea and Brazil


  • Co-author, “Focusing On Private Equity: Global Merger Control Implications”, Competition Policy International Antitrust Chronicle (January 2018)
  • Co-author, United States Law and Practice Chapter, Chambers Global Practice Guides: Merger Control (2018) 
  • Co-author, “Hart-Scott-Rodino: The Year Ahead,” Law360 (January 26, 2016)
  • Interview, “A Discussion with the FTC’s Premerger Notification Office,” The Threshold (Fall/Winter 2015)
  • Quoted, “Third Point ruling sparks calls for reporting reform,” HFM Week (September 25, 2015)
  • Co-author, “A Narrowing Of The HSR Investment-Only ExemptionLaw360 (September 9, 2015)
  • Co-Author, “Teva, Mylan And The Impact Of 'Foreign' On HSR Analysis,” Law360 (July 8, 2015)
  • Co-author, “7 HSR Filing Reminders From Berkshire Hathaway Case,” Law360 (September 26, 2014)
  • Co-Author “Minority acquisitions and merger control: a way forward for the EU,” Global Competition Review (January 9, 2014)
  • Co-author "HSR Rule Changes: A Look Back (and Ahead)," CPI Antitrust Chronicle (May 2013)


  • Presenter, “Private Equity and Antitrust,” American Bar Association (May 4, 2017)
  • Presenter, “International Merger Control: An Update from the BRICs for US Client,” The Knowledge Group (May 19, 2015)
  • Presenter, “Patent Acquisitions – When Are They HSR Reportable?”, The Knowledge Group (April 9, 2014)
  • Presenter, “New HSR Act Rules for Pharmaceutical Licensing TeleBriefing,” Law Seminars International (January 15, 2014)
  • Presenter, “Antitrust and Healthcare Transactions,” webinar (July 2012)
  • Presenter, “Closing Your Deal: What Sponsors Need to Know about Premerger Developments in ‘Hot’ Jurisdictions,” webinar (April 2013)
  • JD, Northeastern University School of Law, 1998
  • BS (English), summa cum laude, Boston College, 1995; Phi Beta Kappa; Golden Key National Honor Society
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