Four fire engines and around 25 firefighters tackled a fire at a semi-detached maisonette on Chancellor Gardens in Croydon.
The first floor was destroyed by the fire. One man left the building before the Brigade arrived and was taken to hospital by London Ambulance Service.
Control Officers took the first of four calls at 2135 and mobilised crews from Purley, Croydon and Wallington fire stations to the scene. The incident was over for firefighters at 2301.
The cause of the fire has been recorded as undetermined.