Four fire engines and around 20 firefighters were called to a fire in a flat on Gap Road in Wimbledon Saturday afternoon.
A woman escaped from a neighbouring flat before firefighters arrived on the scene. She was suffering from smoke inhalation and was treated by London Ambulance Service crews at the scene.
The fire damaged part of a second floor flat.
The Brigade was called at 0152 and the fire was under control by 0255.
Fire crews from Wandswoth, Wimbledon and Tooting fire stations were at the scene.
The cause of the fire is under investigation.