Six fire engines and around 40 firefighters were called to a fire at a block of flats in Portland Grove, Stockwell.
Part of a flat on the 14th floor was damaged by fire. Around 50 people left the building before the arrival of the Brigade. One woman was treated at the scene by London Ambulance Service crews before being taken to hospital.
The Brigade was called at 0952 and the fire was under control at 1104. Fire crews from Brixton, Lambeth and Clapham fire stations attended the scene.
The cause of the fire is under investigation.