Four fire engines and 21 firefighters and officers were called to a fire at a house in Mandrake Road, Upper Tooting.
A small part of the kitchen of the semi-detached house was damaged by the fire. One man was rescued from the ground floor by crews wearing breathing apparatus. He was treated at the scene by London Ambulance Service crews.
Station Manager Graeme Hunter, who was at the scene, said: "A neighbour raised the alarm to this fire after hearing a smoke alarm sounding.
"This goes to show how important it is to have smoke alarms fitted throughout your property.
"Smoke alarms should be fitted in all rooms in the home and kitchens should be fitted with heat alarms.
"All alarms in the home should be tested regularly - at least once a month and when you return from holiday.”
The Brigade was called at 0346 and the fire was under control at 0431. Fire crews from Tooting, Wimbledon and Clapham fire stations attended the scene.
The cause of the fire is under investigation.