Six fire engines and around 40 firefighters tackled a fire at a hostel on Great Peter Street in Westminster.
A third-floor bedroom was destroyed by fire. Around 40 people left the building before the Brigade arrived. There were no reports of any injuries.
The Brigade's 999 Control Officers took 10 calls to the blaze.
The Brigade was called at 1351 and the fire was under control by 1436. Fire crews from Euston, Brixton, Clapham, Lambeth, Battersea and Hammersmith fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.