Four fire engines and around 25 firefighters tackled a fire at an office building on Abbey Road in Park Royal.
An electrical cupboard on the third floor of the seven-storey building was partially damaged by fire. There were no injuries.
The Brigade was called at 2032 and the fire was under control by 2148. Crews from Park Royal, Acton, Wembley and Willesden fire stations attended the scene.
The fire is believed to be accidental and caused by an electrical event.