Two fire engines and around 10 firefighters were called to a fire at a maisonette on Idlecombe Road in Tooting.
Part of a ground floor maisonette was damaged by fire. Firefighters led one woman to safety. She was treated on scene for smoke inhalation and taken to hospital by London Ambulance Service crews.
The Brigade was called at 1116 and the fire was under control by 1142. Fire crews from Wimbledon and West Norwood fire stations attended the scene.
The cause of the fire is under investigation.