Six fire engines and around 40 firefighters tackled a fire at a commercial building on Mortimer Street in Fitzrovia.
Part of a room at basement-level was damaged by fire. There were no reports of any injuries.
The fire caused smoke logging in the building, so crews used positive pressure ventilation fans to help clear smoke quickly.
The Brigade was called at 1646 and the fire was under control by 1833. Fire crews from Soho, Islington, Shoreditch, Lambeth and Euston fire stations attended the scene.
The cause of the fire is believed to have been electrical.