Dentons

Employment and Labour

Partner

John Mastoras is a partner in our national Employment and Labour group. He is a leading advocate, renowned for litigating complex labour and employment disputes and offering strategic and innovative counsel to prominent businesses and employer associations across Canada.

John advises employers in unionized and non-unionized workplaces, including federally and provincially regulated operations, on matters that require practical, commercially focused solutions. He also routinely provides strategic counsel in connection with workplace policy development, restructuring, human rights, occupational health and safety, workplace safety and insurance, labour injunctions and common law employment actions.

As a recognized authority in labour arbitration, labour relations board proceedings and collective bargaining, John regularly represents employers before boards of arbitration and labour relations tribunals and has served as employer nominee on boards of arbitration in proceedings under the Ontario Hospital Labour Disputes Arbitration Act.

His experience spans a broad range of industries, including energy, healthcare, pharmaceuticals, transportation, technology, retail grocery, longshoring, building services, pulp and paper, and manufacturing. This sector breadth enables him to anticipate operational and workforce pressures and tailor labour and employment strategies to each client’s regulatory environment, workforce structure and business objectives.

John has a distinguished reputation, reflected in numerous industry accolades. He recently received the 2026 Sefton-Williams Award, conferred by the University of Toronto to recognize individuals who have made significant, lasting contributions to the field of labour relations and human rights. He taught for 20 years as an Adjunct Professor at the University of Toronto’s Centre for Industrial Relations and Human Resources (CIRHR) and received the 2009 Morley Gunderson Prize for outstanding professional achievement and significant service to CIRHR.

John frequently shares his insights on collective bargaining trends in Canada with labour relations thought leadership groups such as the Global LERN Centre of Excellence, and he routinely provides legal updates and analysis to the CHRO Association on the Canadian labour and employment landscape.