Four fire engines and around 25 firefighters tackled a fire at a spa with flats above on Edgware Road.
A clothes dryer in the spa was destroyed by fire. There were no reports of any injuries.
The Brigade was called at 0150 and the fire was under control by 0245. Fire crews from Paddington, Euston and North Kensington fire stations attended the scene.
The cause of the fire is under investigation.