An employee at Haymishe Bagel Shop called in the fire at 10:13 a.m.
When firefighters got to the scene at 3031 Bathurst St.,flames were coming out of the front of the bagel shop.
They quickly evacuated the building, and then worked to bring the three-alarm fire under control.
Capt. Mike Strapko told CBC News that dozens of firefighters were dispatched to the scene at the height of the fire, which sent smoke billowing into the air that could be seen over the Toronto skyline.
"Just after 11 a.m., part of the first floor had collapsed into the basement, due to the heat and water from the fire," Strapko said in a telephone interview on Sunday morning.
Firefighters worked to keep the fire from spreading to a nearby business. They remained at the scene throughout the afternoon and into Sunday evening.
The full damage from the fire was not immediately known.
The fire marshal is due to visit the site on Monday.