Four fire engines and around 25 firefighters were called to a basement fire at a house on Salcott Road in Battersea.
Part of the basement and ground floor was damaged by the blaze.
A man left the building before the Brigade arrived. He was suffering from smoke inhalation and treated by London Ambulance Service crews.
The Brigade was called at 0230 and the fire was under control by 0351. Firefighters from Battersea, Clapham, Wandsworth and Tooting fire stations were at the scene. The cause of the fire is under investigation.