Four fire engines and 21 firefighters and officers were called to a fire at a house converted into flats in Raul Road, Peckham.
Part of the second floor was damaged by fire. Three people left the property before the arrival of the Brigade.
The Brigade was called at 0315 and the fire was under control at 0443. Fire crews from Peckham, New Cross, Old Kent Road and Brixton fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.