SEIU Healthcare is a Canadian trade union representing more than 60,000 workers in Ontario, Canada. Through collective bargaining, the union represents workers in hospitals, home care, nursing and retirement homes, and community services. The union has been active in Ontario for over 70 years.

SEIU Healthcare is distinct from SEIU Local 2 Canada, albeit both SEIU Healthcare and Local 2 are affiliated with SEIU.

After several years of pressure from its parent union SEIU and its campaign to restructure including merging eight Canadian SEIU locals into a mega Local 1. Instead, The merger was mired with controversy, with 8 SEIU locals representing 30,000 members (half of SEIU members in Ontario) voting to disaffiliate from the SEIU and join the Canadian Auto Workers (CAW) instead. SEIU responded by placing six of the locals under trusteeship, and prevented them from transferring en masse. CAW responded by raiding individual bargaining units over 181 union raid elections. This resulted in a loss of 14,000 SEIU members, which led to allegations by the Canadian Labour Congress that CAW was raiding.

Since 2004, the union's governing structure and membership servicing has been based on a mega-local and business union model. SEIU's organizational structure and leadership has been criticized by several labour activists as undemocratic and bureaucratic.

The majority of SEIU Healthcare's units do not have the right to strike, as they are bound by Ontario's Hospital Labour Disputes Arbitration Act (HLDAA).

SEIU Healthcare's constitution does not provide any unit autonomy, and gives a significant amount of executive power to its officers. SEIU International itself has recognized this criticism.

In 2013, SEIU Local 1 Ontario rebranded itself and changed its name to SEIU Healthcare to publicly appeal to the patients, residents and clients that are taken care of by SEIU workers in the healthcare sector.