The Honourable Thomas Cromwell obtained music and law degrees from Queen's before receiving a graduate law degree (B.C.L.) from Oxford. He practiced law in Kingston and Toronto and taught at the Faculty of Law, Dalhousie University. During his time at Dalhousie, he was active as a labour arbitrator and served as vice-chair of the Nova Scotia Labour Relations Board. He served as executive legal officer to the Chief Justice Canada from 1992 to 1995 and was appointed a judge of the Nova Scotia Court of Appeal in 1997. He served there until his appointment to the Supreme Court of Canada in 2008.
Mr. Cromwell has served as chair or president of three national organizations: The Canadian Association of Law Teachers, The Canadian Institute for the Administration of Justice, The Canadian Forum on Civil Justice, and continues to serve as chair of the Action Committee on Access to Justice in Civil and Family Matters.
Mr. Cromwell was the first recipient of the Canadian Bar Association's Louis St. Laurent Award of Excellence and is an honorary fellow of Exeter College, Oxford, the American College of Trial Lawyers, and CREATE Justice at the University of Saskatchewan. He is an honorary director of the Canadian Institute for the Administration of Justice and the recipient of four honorary doctorates in law. An award in his name, The Honourable Thomas Cromwell Award for Public Service, has been established by the Queen's law faculty. He retired from the Supreme Court of Canada on 1 September 2016. The Pierre Elliott Trudeau Foundation appointed him a Trudeau mentor in 2017.