Eight fire engines and around 60 firefighters tackled a flat fire on Bartholomew Close in Barbican.
Most of a four-roomed flat on the third floor of a residential building was damaged by fire. Part of another flat on the fourth floor was also damaged by the blaze. One man left the building before the Brigade arrived and was taken to hospital by London Ambulance Service crews.
The Brigade's 999 Control Officers took more than 35 calls to the blaze.
Station Commander Steve Howlett, who was at the scene, said: "Firefighters worked incredibly hard to ensure everyone was accounted for and there were no remaining hot spots.
"The Brigade's Drone Team were able to use drones to survey the incident from above and relay images of hard-to-reach areas to incident commanders."
The Brigade was called at 1558 and the fire was under control by 1813. Fire crews from Soho, East Greenwich, Lambeth and surrounding fire stations attended the scene.
The cause of the fire is under investigation.