Six fire engines and around 40 firefighters tackled a house fire on Fortis Green Avenue in East Finchley.
Part of the ground and first floors of a two-storey terraced house was damaged by fire. Half of the house's loft, that has been converted into flats, along with half of the property's roof was also damaged by fire.
Three adults and two children from the property and a neighbouring property were treated by London Ambulance Service crews for smoke inhalation.
The Brigade's 999 Control Officers received nine calls about the fire.
The Brigade was called at 0442 and the fire was under control by 0838. Crews from Hornsey, Finchley, Holloway, Tottenham and surrounding fire stations attended the scene.
The cause of the fire is under investigation.