Four fire engines and around 25 firefighters were called to a fire at a block of flats on Gorman Road in Greenwich.
Most of a ground floor flat in a two-storey block was damaged by the fire. One man left the building before the Brigade arrived. He was treated for smoke inhalation at the scene by London Ambulance Service crews.
The Brigade's 999 Control Officers took 11 calls to the blaze.
The Brigade was called at 1716 and the fire was under control by 1828. Fire crews from Plumstead and East Greenwich fire stations were at the scene.
The cause of the fire is under investigation.