Four fire engines and around 25 firefighters were called to a fire at a terraced block of flats on North Hill in Highgate.
Part of a three-roomed flat on the first floor of the building was damaged by fire. Three people self-evacuated and one man was taken to hospital by London Ambulance Service crews.
The Brigade was called at 0807 and the fire was under control by 0855. Fire crews from Hornsey and Finchley fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.