Four fire engines and around 25 firefighters were called to a fire at a mid-terrace maisonette on Goldsboro Road in Stockwell.
Around half of the first floor of the maisonette in a two-storey building was damaged by fire.
Fortunately, smoke alarms in the property alerted the residents to the fire and they were able to get out of the property before the arrival of the Brigade.
One man and one woman were treated for smoke inhalation at the scene by London Ambulance Service crews.
The Brigade’s fire investigators believe the fire was caused by an unattended candle.
A London Fire Brigade spokesperson said: “This incident shows just how important it is to have working smoke alarms. Thankfully, smoke alarms fitted inside the property were able to give the earliest possible warning to the fire, providing residents time to escape.
“Candles are one of the most common causes of fire. It’s really important that you never leave a candle unattended and keep them away from curtains and anything else that can easily catch fire.
“You should also ensure they are in a heat-resistant holder and placed on a stable surface so they won’t be knocked over.”
The Brigade was called at 1824 and the fire was under control by 1944. Fire crews from Lambeth and Clapham fire stations attended the scene.