Four fire engines and around 25 firefighters were called to a flat fire above a shop on Rye Lane in Peckham.
Part of a three roomed flat on the first floor was destroyed by fire.
The Brigade was called at 0854 and the incident was under control by 0930. Fire crews from Peckham, New Cross, Old Kent Road and Brixton fire stations were in attendance.
The cause of the fire is under investigation.