Six fire engines and around 40 firefighters responded to a fire on Marylebone Road, Marylebone.
The incident occurred in a mixed-use building of nine floors. The basement of commercial unit, being used as part of a spa, was damaged by the fire.
The Brigade was first called about the incident at 1052, and crews from Soho, North Kensington, Kensington and surrounding fire stations were sent to the scene. Crews were able to bring the fire under control by 1134.
The cause of the fire is under investigation.