The two-alarm fire broke out in a unit at 2415 Jane St. at around 1:30 a.m.
Firefighters encountered heavy smoke and flames when they arrived on the fourth floor.
A woman believed to be in her 60s was taken to hospital in serious condition but is expected to survive.
A dog was also rescued from a small cage inside the apartment. Firefighters found the dog lifeless but were able to revive it using oxygen.
The dog is doing well in the care of Toronto Animal Services.