Five fire engines and around 35 firefighters were called to a fire at a block of flats on Liston Way in Woodford Green.
Part of a room in a flat on the ninth floor was damaged in the blaze.
Two men left the property before the Brigade arrived. A further forty people in the block also evacuated before crews arrived. One man was treated on scene by London Ambulance Service crews and taken to hospital.
The Brigade's Fire Investigators believe the fire was caused by cooking which was left unattended.
A London Fire Brigade spokesperson said: "Cooking is one of the most common causes of fire in the home.
“We would like to remind the public to never leave cooking unattended – if you have to leave the room or the house, turn the heat off."
The Brigade was called at 1359 and the fire was under control by 1507. Fire crews from Hainault, Leytonstone, Woodford, Chingford and Ilford fire stations attended the scene.