Six fire engines and around 40 firefighters were called to a maisonette fire on Portpool Lane, EC1N.
Most of the sixth floor and part of the roof of the building were damaged by fire.
Two men left the property before the Brigade arrived. They were both suffering from smoke inhalation and treated by London Ambulance Service crews.
The fire was very visible and the Brigade control took 21 999 calls.
The Brigade was called at 1523 and the fire was under control by 1703. Fire crews from Shoreditch, Islington, Whitechapel, Soho and Lambeth fire stations attended the scene.
The cause of the fire is under investigation.