Thomas N. O’Connor

Active Retired Partner
781.359.9010 | 781.359.9001 |

Tom is a founder of, and of counsel to, the firm, and focuses his practice in complex business litigation.

He has been litigating since 1979 and was formerly a Senior Partner of Hale and Dorr LLP (now WilmerHale), where he was founder and chairman of the debtor/creditor practice group. Tom has extensive experience with workouts and insolvency litigation. In addition to his work for clients of OCM, Tom was a founder, and the general counsel and chief operating officer of Marathon Capital Group LLC, a federally registered investment management firm, which had over $600 million in assets when he sold his interest in the business in 2008. Tom is also currently general counsel of Baystate Financial Services, LLC, one of New England’s oldest and largest financial firms. Tom’s experience as a principal and general counsel in the financial services industry gives him unique insight when representing clients with financial services issues. Tom also has extensive experience serving as an arbitrator, receiver and trustee.

Some highlights of Tom’s practice include:

  • Leading the prosecution of claims before the Financial Industry Regulatory Authority (“FINRA”) brought by a number of injured investors, including claims for unsuitability, failure to execute and unauthorized trading.
  • Leading the prosecution of claims before FINRA brought by injured investors for misrepresentation in connection with the sale of auction rate securities.
  • Serving as lead counsel for ProCD in the precedent-setting case, ProCD v. Zeidenberg, in which the 7th Circuit Court of Appeals held for the first time that shrinkwrap licenses are valid and enforceable and not preempted by federal copyright law.
  • Representing numerous clients in complex commercial cases involving fraud, international commercial transactions and letters of credit, employee theft, workouts, intellectual property and fraudulent conveyances, among others.
  • Representing a major investment company in the defense against a class action in the federal court in Massachusetts asserting claims under the Investment Advisors Act of 1940 and state law.
  • Representing a major investment company in the defense against a class action in the federal court in Massachusetts asserting federal and state law securities claims based upon misrepresentation, fraud and breach of fiduciary duties.
  • Leading the defense of the owner of a significant interest in a real estate venture, structured as a limited liability company, involving fiduciary duty and capital account issues.

Work Experience

O’Connor, Carnathan and Mack, LLC Partner
Quigley, O’Connor and Carnathan, LLC Partner
Marathon Capital Group, LLC General Counsel and COO
Hale and Dorr, LLP Senior Partner
Rogers & Wells Litigation Associate


  • AAA Commercial Arbitration Panel, N.E. District

Honors and Awards

  • Martindale Hubbell AV Rating
  • Massachusetts Super Lawyer
    • 2005, 2008 to date


  • J.D., Albany Law School of Union
  • University B.A., St. Lawrence University

Bar Admission

  • Massachusetts
  • New York
  • Maine