Four fire engines and around 25 firefighters tackled a fire at a house on Penderyn Road in Holloway.
Half of the second floor of a three-storey mid-terraced house was damaged by fire. Three adults and two children left the property before firefighters arrived. They were left in the care of London Ambulance Service crews.
The Brigade's 999 Control Officers received seven calls about the fire.
The Brigade was called at 0808 and the fire was under control by 0929. Crews from Holloway, Kentish Town, Islington and Soho fire stations attended the scene.
The fire is being treated as accidental and is believed to have been caused by an electrical fault.