Four fire engines and around 25 firefighters were called to a house fire on Moffat Road in Thornton Heath.
Half of the ground floor of a mid-terrace house was damaged by fire. Two adults and three children left the building before the Brigade arrived and were taken to hospital by London Ambulance Service crews.
The Brigade was called at 3.54am and the fire was under control by 5.03am Fire crews from Norbury, West Norwood, Woodside and Croydon fire stations attended the scene.
The cause of the fire is under investigation.