The Toronto Transit Commission's board has voted in favour of making face coverings mandatory for all customers starting July 2.
The TTC says exemptions will also be made for children under two years of age and for those who have medical considerations or are unable to put on or take off a face covering.
The board says that TTC employees who work behind a physical shield or in areas not accessible to the public are also exempt.
A statement from the TTC says that it doesn't believe that strict enforcement will be necessary, but compliance rates will be monitored.
The TTC says it's taking other measures to slow the spread of COVID-19 including conducting multiple vehicle and station cleanings each day, equipping subway stations with hand sanitizer dispensers.
It says it's also installing barriers and signage to remind customers to keep their distance from operators.