The injured firefighter was taken to Sunnybrook Hospital with first- and second-degree burns to his hands, waist and stomach, CBC's Colin Butler reported from the scene. The injuries are not life-threatening.
Toronto firefighters said the blaze at 30 Denton Avenue, near Danforth and Victoria Park avenues, started on a balcony of the building.
The fire, which is out, was called in at 6:44 p.m. ET.
Butler reported at about 8:50 p.m. that there was still smoke inside the building, as residents waited outside on the lawn or on their balconies.