Five fire engines and around 30 firefighters attended a fire at a residential block on Portland Place in Marylebone.
The fire occurred in a maisonette situated within the basement and on the ground floor of the building. There were no reports of any injuries.
The Brigade was called at 0752 and Control Officers mobilised crews from Euston, Soho and Paddington fire stations to the scene. The fire was extinguished by 0919.
The cause of the fire is under investigation.