Four fire engines and 21 firefighters and officers were called to a fire at a block of flats in Larkhall Lane, Stockwell.
Most of a second floor flat was damaged in the fire. A small part of a third-floor flat and the external fittings of the roof were also damaged in the blaze. One man treated by London Ambulance Service at the scene and taken to hospital as a precaution.
The Brigade was called at 1524 and the fire was under control at 1645. Fire crews from Brixton, Clapham, and Lambeth fire stations attended the scene.
The cause of the fire is under investigation.