The blaze at St Mary's Church Hall on St Alphonsus Road in Clapham early on Tuesday has prompted crews to warn against leaving flames unattended.
A spokesperson for London Fire Brigade said: "Candles are one of the most common causes of fire.
"It's really important that you never leave a candle unattended and put them out before going to sleep.
"Candles should be kept well away from curtains and anything else that can easily catch fire."
Candle warning issued following #Clapham church hall fire, one man leaves building before crews arrive https://t.co/rPwlC2UwMT pic.twitter.com/JaWkEzXT7r
— London Fire Brigade (@LondonFire) November 21, 2017
One person was treated by paramedics at the scene for smoke inhalation after flames damaged a room on the first floor of the two and three-storey building.
Crews from fire stations in Clapham, Brixton and Battersea were called to St Mary's Church Hall shortly before 5.30am on Tuesday.
They say the fire was under control by 6.36am.