Four fire engines and around 25 firefighters were called to a fire at a flat on Dorrien Walk in Streatham Hill.
Part of a three-roomed flat on the first floor was damaged by fire. Firefighters wearing breathing apparatus rescued one woman from the building. She was treated on scene by London Ambulance Service crews.
The Brigade was called at 0912 and the fire was under control by 0941. Fire crews from West Norwood and Tooting fire stations attended the scene.
The cause of the fire is under investigation.