Four fire engines and around 25 firefighters tackled a fire on Brentfield in Stonebridge Park.
Part of a converted vehicle workshop beneath a disused office block was damaged by fire. One vehicle was destroyed by fire. There were no reports of any injuries.
The Brigade's 999 Control Officers received five calls about the fire.
The Brigade was called at 0044 and the fire was brought under control by 0208. Crews from Park Royal, Wembley and Willesden fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and Metropolitan Police.