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Mark A. Berthiaume focuses his practice in the representation of clients in white collar criminal matters, government investigations, and complex civil litigation, including the defense of class actions. Mark has represented corporations and individuals in government investigations of securities fraud, antitrust violations, bank fraud, health care fraud, mail and wire fraud, and immigration law violations. Mark also represents clients involved in federal civil rights actions under 42 U.S.C. Section 1983 and related claims including wrongful death. Much of his practice also concentrates on international, national and regional corporate clients and their officers and directors in complex civil litigation involving securities, intellectual property, real estate, construction, and telecommunications-related disputes. Mark, a former Assistant U.S. Attorney, is an experienced trial lawyer, practicing in the U.S. Supreme Court, as well as U.S. Courts of Appeals and U.S. District Courts.


  • Securities fraud
  • Antitrust violations
  • Bank fraud
  • Health care fraud
  • Mail and wire fraud
  • Civil rights actions
  • Immigration law violations
  • Violations of the Foreign Corrupt Practices Act



  • Secured a $1.1 million judgment in favor of a financial services company and related independent broker dealer after a FINRA arbitration hearing, along with the dismissal of all counterclaims seeking several million dollars in damages.
  • Represented national publicly owned media company in connection with an internal corporate investigation of its business practices.°
  • Represented one of the country's largest privately owned corporations in connection with a criminal investigation of alleged price fixing by the Justice Department's Antitrust Division of the U.S. Department of Justice.°
  • Represented former Chief Financial Officer of publicly traded company in an SEC investigation of backdating of stock options.
  • Represented the audit committee of a publicly traded company in an internal corporate investigation of potential securities law violations for purposes of Sarbanes-Oxley compliance.
  • Represented senior executives of a national health care provider that was the target of a Medicare fraud investigation conducted by the U.S. Attorney's Office for the District of Massachusetts.
  • Represented one of the country's largest retailers in connection with an internal corporate investigation of potential immigration law violations.°
  • Represented company and its Chief Executive Officer in a terrorism-related investigation involving alleged violations of the Patriot Act.
  • Conducted an internal investigation for an independent trading technology firm and agency broker after a whistleblower raised various allegations of fraud, including securities and accounting fraud. The conclusions reached through the investigation were subsequently upheld in litigation brought against the company by the whistleblower.
  • Represented the former controller of a publicly traded technology company before the Securities & Exchange Commission’s enforcement division in connection with a stock option back-dating investigation.
  • Secured, after a 2 ½ week jury trial, the complete dismissal of claims of fraud and breach of fiduciary duty against a Boston real estate investment firm and various of its officers and directors.
  • Represented defendant in securities fraud class action in the biotech industry.
  • Represented senior officer of a public company in defense of criminal securities fraud indictment.
  • Secured the dismissal of a securities fraud class-action complaint brought against the former general counsel of a publicly traded pharmaceutical company in the U.S. District Court for the District of Massachusetts. The dismissal was subsequently affirmed by the U.S. Court of Appeals for the First Circuit. See New Jersey Carpenters Pension v. Biogen Idec Inc., 537 F.3d 35 (1st Cir. 2008).
  • Secured a jury verdict of $1.1 million, after a two-week trial in the U.S. District Court for the District of Massachusetts, on behalf of a national, publicly traded retailer on claims of breach of non-competition, non-solicitation and confidentiality agreements by a former executive. See Casual Male Retail Group. Inc. et al. v. Robert H. Yarbrough. et al., Civil Action No. 05-CV -12049-NMG.
  • Represented a publicly traded power technology company and its then-new CEO in an action brought by the CEO’s former employer seeking to enforce a non-competition agreement.
  • Represented national retailer in litigation involving misappropriation of trade secrets and breach of non-competition agreements through trial.
  • Secured the dismissal of assault and battery charges brought against a former NHL player, coach, and general manager, now a current high-profile, international television personality, at the probable cause stage.
°The above representations were handled by Mr. Berthiaume prior to his joining Greenberg Traurig, LLP.

Recognition & Leadership

  • Listed, The Best Lawyers in America, Commercial Litigation, 2020-2024
  • Listed, Boston magazine, "Top Lawyers - Commercial Litigation," 2022-2023
  • Listed, Super Lawyers magazine, Massachusetts Super Lawyers, 2013-2015
  • Rated, AV Preeminent® 5.0 out of 5.0

°AV®, AV Preeminent®, Martindale-Hubbell DistinguishedSM and Martindale-Hubbell NotableSM are certification marks used under license in accordance with the Martindale-Hubbell® certification procedures, standards and policies.

  • Member, American Bar Association
  • Member, Boston Bar Association
  • Member, Massachusetts Bar Association


  • J.D., The George Washington University Law School, 1980
  • B.A., magna cum laude, Dartmouth College, 1977
  • Massachusetts
  • Supreme Court of the United States
  • U.S. Court of Appeals for the Federal Circuit
  • U.S. Court of Appeals for the First Circuit
  • U.S. Court of Appeals for the Fourth Circuit
  • U.S. District Court for the District of Maryland
  • U.S. District Court for the District of Massachusetts