Fifteen fire engines and around 100 firefighters were called to a fire at a block of flats on the Grange Estate in East Finchley.
The roof of the building and part of the second floor of the three-storey building were damaged by the fire. Around 60 people left the building before the Brigade arrived. There were no reports of any injuries.
Station Manager Peter Gustafson, who was at the scene, said: "When crews arrived they were faced with a well developed fire in the roof space of the building."
The Brigade was called at 0002 and the fire was under control by 0205, but firefighters remained on scene throughout the evening damping down. Fire crews from Barnet, Hornsey, Southgate, Holloway, Kentish Town and surrounding fire stations attended the scene.
The Brigade's 999 Control Officers took 15 calls to the fire.
The cause of the fire is under investigation.