Sean T. Carnathan

Sean T. Carnathan is a partner and founder of O’Connor, Carnathan and Mack, LLC in Burlington, Massachusetts, focusing on complex business litigation. His practice emphasizes insurance coverage, closely held businesses, and trust and estate litigation. He represents policyholders, financial institutions, investment funds, executives, and owners of closely held companies. His work spans commercial, real estate, construction, employment-contract, non-compete, and insurance disputes in state and federal courts across multiple jurisdictions.

Sean earned an LL.M. from Harvard Law School, a J.D., summa cum laude, from the University of Maine School of Law, and an A.B., magna cum laude, from Bowdoin College. He also served as an Ames Fellow at Harvard Law School and clerked for Justice Paul L. Rudman of the Maine Supreme Judicial Court. This academic and judicial background supports his work on complex disputes involving detailed records, contractual duties, and contested legal issues.

Sean has tried or arbitrated more than twenty-five matters in state and federal courts in Connecticut, Delaware, Maine, Massachusetts, and New Hampshire. His representative results include a $24 million summary judgment in a trust fund dispute, a $5 million contract verdict, and multimillion-dollar settlements involving trade secrets, insurance, and intercreditor issues. He also regularly advises corporate executives on employment agreements and non-compete obligations and serves as a neutral with AMANDA ADR.

Sean T. Carnathan has received recognition for insurance litigation, insurance law, and trusts and estates litigation, including listings in Best Lawyers in America. He has also been selected as a Massachusetts Super Lawyer and holds a Martindale-Hubbell Preeminent rating. His writing includes Massachusetts Bad Faith Insurance Litigation and publications addressing insurers’ duties to defend and indemnify. He combines extensive courtroom experience with practical counseling and dispute-resolution judgment for clients facing high-stakes commercial conflicts.

Law Office Affiliations

• Partner, O’Connor, Carnathan & Mack, LLC
• Member, Massachusetts Bar Association
• Member, Maine State Bar Association
• Member, New Hampshire Bar Association
• Hearing Officer to Present, Massachusetts Board of Bar Overseers (2015-2020)
• Member, Trial Law Institute of the Litigation Counsel of America
• Member, Diversity Law Institute of the Litigation Counsel of America
• Neutral, AMANDA ADR

Licensed State

• Massachusetts
• Maine
• New Hampshire

Education

• Harvard Law School
  Master of Laws (LLM)
• University of Maine School of Law
  Juris Doctor (JD) (Summa Cum Laude)
• Bowdoin College
  A.B. (Magna Cum Laude)

Awards & Badges