Four fire engines and around 25 firefighters tackled a flat fire on Dog Kennel Hill in Dulwich.
Most of a first-floor flat above a barber shop was damaged by fire. There were no reports of any injuries.
The Brigade was called at 2244 and crews from Peckham, New Cross and Old Kent Road fire stations attended the scene. The fire was under control by 2330.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.