Four fire engines and around 25 firefighters were called to a fire at a flat on Dudden Hill Lane in Willesden.
Half of a balcony on the first floor was damaged by fire and half of the external fascia of the building and the roof were also damaged by the blaze. One man was treated on scene by London Ambulance Service crews.
The Brigade was called at 2139 and the fire was under control by 2318. Fire crews from Willesden, Park Royal, West Hampstead and Wembley fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.