Four fire engines and around 25 firefighters were called to a fire at a flat on Exhibition Way in Wembley.
Half of a five-roomed flat on the second floor of the building was damaged by fire. There were no reports of any injuries.
The Brigade was called at 0808 and the fire was under control by 0837. Fire crews from Wembley, Park Royal, Willesden and Stanmore fire stations attended the scene.
The cause of the fire is under investigation.