About Mark

Mark Sheeley's litigation practice spans corporate-commercial disputes, including complex contract disagreements, class actions, tax litigation, intricate financial matters and insolvency proceedings. He is committed to identifying practical outcomes for clients, whether the matter is resolved in the courtroom or the boardroom. Sheeley co-leads Osler's case assessment team, which analyzes and values complex disputes for clients. He has appeared before courts across Canada, including Ontario's Commercial List, the Court of Appeal for Ontario, the Tax Court of Canada, and ultimately the Supreme Court of Canada. His matters have included acting for Cameco Corporation in a transfer pricing case before the Tax Court of Canada, later upheld on appeal, and for Loblaw Companies Limited in a tax dispute concerning its international financial affiliate. He holds a J.D. from Osgoode Hall Law School, an M.A. from the University of Western Ontario and a B.Sc. (Hons.) from the University of Victoria.

Education & credentials

Law school
Osgoode Hall Law School

Listing compiled from public sources in July 2026. Confirm Mark Sheeley’s licence and standing in the Law Society of Ontario directory ↗