Twelve fire engines and around 80 firefighters were called to a flat fire on Howick Place in Westminster.
Half of a third-floor apartment was damaged by fire and part of the roof was also damaged by the blaze. Around 150 people left the building before the Brigade arrived. There were no reports of any injuries.
Firefighters carried out salvage operations to mitigate damage to other areas of the building.
There was heavy traffic disruption on the surrounding roads, therefore people were advised to avoid the area.
The Brigade was called at 1253 and the fire was under control at 1755. Fire crews from Soho, Chelsea, Euston and other surrounding fire stations attended the scene.
The cause of the fire is believed to have been accidental, but the exact cause remains under investigation.