Four fire engines and around 25 firefighters tackled a flat fire on Chicheley Street in Waterloo.
A small part of a mattress in the bedroom of a flat on the second floor was damaged by fire. There were no reports of any injuries.
The fire is believed to have been accidentally caused by hair straighteners on bedding.
A London Fire Brigade spokesperson said: "Remember that hairdryers, hair tongs, and straighteners can get extremely hot, so it’s very important to remember to switch them off and leave them to cool on a heatproof surface.
"Firefighters recommend that you have a look at our online Home Fire Safety Checker to make sure there are no hidden hazards in your home.
“The online tool will ask you a series of questions that will help us work out the level of risk in your home, or the home of someone you care for. It only takes a few minutes to get tailored advice to keep yourself and loved ones safe from fire.”
The Brigade was called at 2031 and the fire was under control by 2112. Fire crews from Soho, Dowgate and Euston fire stations attended the scene.