Fire crews wearing breathing apparatus rescued an elderly man from a flat on Reedworth Street in Lambeth on Saturday afternoon.
The man was taken to hospital by the Helicopter Emergency Medical Service suffering from burns and smoke inhalation.
The fire badly damaged the flat. Fortunately, it was fitted with a working smoke detector and fire alarm.
Four fire engines, 21 firefighters and officers from Brixton, Soho, Dockhead and Old Kent Road fire stations attended the incident.
The Brigade was called at 1544 and the fire was brought under control at 1639.
The cause of the fire is under investigation.