The third-floor apartment is located at the corner of Galt and Laurendeau streets in Montreal's southwest borough.
The fire burned for over an hour before being extinguished around 3:50 p.m. ET.
Police said the woman is in hospital, but they don't fear for her life.
Rosemary Hosson lives across the street and saw the smoke while returning home from an out-of-town Thanksgiving celebration.
“I was coming home from a wonderful weekend away near Tremblant, and as we were coming off the 720 West, I saw billowing smoke, realized it was on my block, panicked, and managed to manoeuvre around my one-way street to get up to my house,” she said.
When she spoke to CBC News at 3:30 p.m. ET, firefighters were still inside and on the roof battling the flames.
Hosson said it appeared as though the balcony was melted and that part of the building was missing.