Four fire engines and around 25 firefighters tackled a fire at a residential block of flats on Lawn Road in Kentish Town.
A two room flat on the ground floor was partially destroyed by fire. Two women, one man and one child were treated by London Ambulance Service for slight smoke inhalation.
The Brigade was called at 2044 and the fire was under control by 2151. Crews from Kentish Town, Holloway and Paddington fire stations attended the scene.
The cause of the fire is under investigation.