Four fire engines and around 20 firefighters and officers were called to a fire at a block of flats in Pytchley Road in East Dulwich.
Part of a flat on the first floor of the building was damaged by fire.
One man left the property before the arrival of the Brigade and was treated at the scene for smoke inhalation before being taken to hospital by London Ambulance Service crews.
The Brigade was called at 1112 and the fire was under control at 1229. Fire crews from New Cross, Old Kent Road, Peckham and Lambeth fire stations attended the scene.
The cause of the fire is under investigation.