Four fire engines and around 25 firefighters were called to a fire at a derelict office on Ealing Green in Ealing.
Part of a single-storey building once used as an office was damaged by fire. There were no reports of any injuries.
The Brigade's 999 Control Officers took 16 calls to the blaze.
The Brigade was called at 1815 and the fire was under control by 1917. Fire crews from Acton, Ealing, Chiswick and Southall fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.