Four fire engines and 21 firefighters and officers were called to a fire at a block of flats in Hodford Road in Golders Green.
Most of the balcony of a second floor flat was damaged by fire. Part of the flat and part of the roof void was damaged by fire.
The Brigade was called at 1947 and the fire was under control at 2050. Fire crews from West Hampstead, Hendon and Willesden fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and Metropolitan Police Service.