Four fire engines and around 25 firefighters were called to a fire at a flat on Dorset Road in Stockwell.
Part of a flat on the fifth and sixth floor was damaged by the blaze. One woman left the property before the Brigade arrived suffering smoke inhalation. She was treated on scene and taken to hospital by London Ambulance Service.
The Brigade was called at 0905 and the fire was under control by 0956 . Fire crews from Lambeth, Brixton and Clapham fire stations attended the incident.
The cause of the fire is under investigation.