Four fire engines and around 25 firefighters were called to a flat fire on York Road in Battersea.
Part of a four-roomed flat on the ground floor of the building was damaged by fire. There were no reports of any injuries.
The Brigade was called at 1805 and the fire was under control by 1842. Fire crews from Battersea, Wandsworth, Fulham and Chelsea fire stations attended the scene.
The Brigade’s Fire Investigators believe the fire was accidental and caused by a fish tank light.