Firefighters contained a fire to a kitchen after the alarm was raised by a smoke detector in a sheltered accommodation block.
Four fire engines and 21 firefighters and officers were called to the fire in Prince of Wales Drive, Battersea.
Part of a flat on the second floor of the four-storey building was damaged. There were no reports of any injuries.
The Brigade was called at 1132 and the fire was under control at 1213. Fire crews from Battersea, Chelsea, Clapham and Fulham fire stations attended the scene.
The cause of the fire is accidental.