Six fire engines and 35 firefighters and officers were called to a fire at a house in Lynette Avenue in Clapham.
Most of the first and second floors of the property were damaged by fire.
Three people left the property before the arrival of the Brigade. There were no reports of any injuries.
Station Manager Nic Myatt, who was at the scene, said: “When crews arrived they were faced by thick, black smoke and had very limited visibility. Firefighters have worked hard in challenging conditions to stop the fire from spreading to neighbouring properties.”
The Brigade was called at 1100 and the fire was under control at 1302. Fire crews from Clapham, Battersea, Tooting and Brixton fire stations attended the scene.
The cause of the fire is under investigation.