Six fire engines and around 40 firefighters attended a fire in a third and fourth floor maisonette on Petten Grove in Orpington.
The fire caused significant damage to both floors of the maisonette.
One woman and a male child were rescued from the fourth floor by firefighters using breathing apparatus and a further female child was rescued by a member of the public from the third floor. All three were taken to hospital by London Ambulance Service.
The Brigade were called at 0737 and the fire was under control at 0858. Fire crews from Orpington, Sidcup and Bromley attended the incident. The cause of the fire is under investigation.