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Brett M. McMahon


Represents clients in a broad range of civil matters, including complex commercial and contractual disputes, professional liability cases and business divorces.

Brett represents clients in a wide array of civil matters in federal and state courts and arbitration proceedings nationwide, including high-stakes commercial and complex contractual disputes, actions against major law firms for legal malpractice and related claims, and litigation involving business divorces and other internal disputes among partners, joint venturers, and limited liability company members.  

Although Brett’s practice spans all industries, he has significant experience representing clients in the legal, media, telecommunications, real estate, cryptoasset, and private equity spaces.

In addition to his defense work, Brett frequently represents individuals and companies on the plaintiff side, including in litigating their claims through trial.  He also regularly advises clients concerning litigation risk in the context of potential transactions and other important business decision-making.

Experience highlights

  • Obtained dismissal of a malpractice action and award of attorneys’ fees in New York state court on behalf of an international law firm
  • Won dismissal of all claims against an international law firm in action asserting claims for fraud, breach of fiduciary duty, and aiding and abetting fraud and breach of fiduciary duty, which was affirmed on appeal
  • Secured favorable settlement of claims for malpractice, breach of duty, tortious interference, and fraud in New York state court on behalf of an international law firm after obtaining dismissal of nearly all claims on a motion to dismiss
  • Favorably resolved malpractice claims in New York state court on behalf of a national law firm arising from the firm’s representation of a former client in a real-estate financing transaction
  • Secured favorable settlement of malpractice claims in New York state court related to tax advice on behalf of an international law firm
  • Favorably resolved action involving allegations of fraud and breach of fiduciary duty against an international law firm in Los Angeles County Superior Court
  • Represented Magnetation LLC as debtor in possession in Chapter 11 proceedings in the Bankruptcy Court for the District of Minnesota, winning approval of the company’s assumption of its only source of revenue, a 20-year supply agreement, after a bench trial
  • Defended Roche in a breach of contract action in Delaware Chancery Court related to milestone payments under a merger agreement
  • Represented prominent Israeli businessman in two bench trials in Delaware Chancery Court arising from a dispute over corporate control of the agricultural-chemical company he founded
  • Secured favorable settlement on behalf of Marquis Energy and its majority shareholders and directors in AAA arbitration involving a dispute over proposed corporate transactions
  • Represented Comcast and certain affiliates in two bench trials in connection with the bankruptcy of a regional sports network
  • Obtained dismissal of RICO claims in federal court on behalf of a major European industrial manufacturing company, which was affirmed on appeal
  • Obtained dismissal of various multi-billion-dollar shareholder derivative and putative class actions in federal court arising out of Morgan Stanley’s subprime mortgage-related write-down
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J.D., University of Southern California Gould School of Law
  • Order of the Coif
  • Senior Editor, Southern California Law Review
B.A., Political Science, University of Richmond
  • cum laude


Law Clerk, Hon. Cynthia M. Rufe, U.S. District Court, E.D. Pennsylvania, 2006-2007

Professional history

  • Davis Polk since 2016

Qualifications and admissions

  • State of New York
  • U.S. Court of Appeals, Fifth Circuit
  • U.S. District Court, E.D. New York
  • U.S. District Court, S.D. New York
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