Six fire engines and around 40 firefighters were called to a flat fire on Maitland Park Road in Chalk Farm.
Part of a four-roomed flat on the ground floor of the building was damaged by fire. A man was rescued by Metropolitan Police Service officers before the Brigade arrived and around 30 people were evacuated from the building. Four people were taken to hospital by London Ambulance Service crews.
The Brigade was called at 0707 and the fire was under control by 0803. Fire crews from Paddington, Islington, Shoreditch, Dowgate and surrounding fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.