Two fire engines and around 10 firefighters were called to a house fire on Bellingham Road in Catford.
Part of the ground floor of a semi-detached house was damaged by fire. Four people left the property before the arrival of the Brigade. Two men and two women were treated for smoke inhalation before being taken to hospital by London Ambulance Service crews.
The Brigade was called at 0612 and the fire was under control by 0726. Fire crews from Lewisham and Forest Hill fire stations attended the scene.
The cause of the fire is under investigation.