With more than 50 years of experience in dispute resolution, Michel Décary has acted on behalf of various clients before the courts of Canada, including the Supreme Court of Canada, and before numerous administrative tribunals. A Fellow of the American College of Trial Lawyers, he is recognized by legal directories in the corporate and commercial litigation, labour and employment law, and administrative and public law categories. Best Lawyers in Canada also named him Lawyer of the Year in 2021 and in 2024 in the corporate governance category.

Michel advises boards, directors and officers of private companies and Crown corporations on matters of corporate governance and civil and criminal liability. He has taught at the École supérieure de régie d'entreprises of the Institute of Corporate Directors of McGill University (2004-2013) and at the training program of the Conseil des administrateurs de sociétés of Université Laval (2005-2012). He sits or has sat on the boards of many public and private companies and various philanthropic organizations.

Michel has been involved in several constitutional and administrative law disputes as counsel for governmental and private parties, including the nationalization of part of the asbestos industry by the Government of Québec, the attempt by the Government of Newfoundland and Labrador to terminate the Churchill Falls electricity contract, challenges to statutes and regulations, including the Competition Act in Alex Couture ltée v. Directeur de la concurrence and in Air Canada v. Attorney General of Canada. He was appointed with Ian Binnie as lead counsel on the legal team defending the first Canada-U.S. free-trade agreement, acted on behalf of the Government of New Brunswick in defence of an attack by Égalité santé en français inc. on the constitutionality of the province's health care reform, and represented Air Canada pilots and employees on the use of French at work.

He has acted as lead counsel or counsel for parties and witnesses before the Cliche, Keable, Malouf, Beaudry, Gomery, Johnson, O'Connor and Charbonneau public commissions of enquiry, as well as before the Commission municipale du Québec, the Autorité des marchés financiers, the Vérificateur général du Québec, coroners, disciplinary boards of various professional orders, arbitration boards and arbitrators. He has regularly acted as a negotiator or attorney for management and labour, and as a mediator or arbitrator.

Michel gives priority to mandates to act as arbitrator in the resolution of disputes between shareholders, directors and officers or in the settlement of labour and employment law disputes, or as counsel in complex corporate, commercial, administrative and constitutional litigation.

He has been awarded the title of King's Counsel and Advocatus Emeritus of the Barreau du Québec, has served as Associate Deputy Minister for Civil and Penal Affairs at the Ministère de la Justice of Québec, and is a member of the Barreau du Québec's administrative committee. He has taught labour law at the Université de Montréal's Faculty of Law, civil law and procedure at the Bar's Continuing Education Services, and pleading techniques at UQAM.