Four fire engines and around 25 firefighters were called to a fire at a house in Russell Road, Tottenham.
Part of the first floor of the house was damaged by fire. Five people left the property before crews arrived and were taken to hospital by London Ambulance Service crews.
The Brigade was called at 0347 and the fire was under control by 0508. Fire Crews from Tottenham, Stoke Newington, Holloway and Walthamstow stations attended the scene.
The cause of the fire is believed to be a fan heater too close to combustible materials.
London Fire Brigade is warning people to take extra care if they use portable heaters, wood burners or open fires this autumn.