Four fire engines and around 20 firefighters and officers were called to a fire at a house in Upton Park Road in Forest Gate.
Half of the ground floor and part of the first floor of the property were damaged by fire.
Four adults and one child left the property before the arrival of the Brigade and were treated for smoke inhalation by London Ambulance Service crews.
The Brigade was called at 2348 and the fire was under control at 0042. Fire crews from Stratford, Plaistow, East Ham and Leytonstone fire stations attended the scene.
The cause of the fire is under investigation.