A flat on Cooks Road in Walworth was badly damaged by fire on Friday afternoon.
No one was injured in the fire, which was confined to the ground floor of a block of flats.
Four fire engines, 21 firefighters and officers from Lambeth, Brixton and Peckham fire stations attended the incident.
The Brigade was called at 1518 and the fire was under control at 1558.
The cause of the fire is under investigation.