Four fire engines and around 25 firefighters were called to a fire in a flat on Zenith Close in Colindale.
Most of a four roomed flat was damaged by fire. One woman and a child were treated at the scene for smoke inhalation by London Ambulance Service crews and taken to hospital.
The Brigade was called at 2305 and the fire was under control by 0035. Fire crews from Hendon, Mill Hill and Stanmore attended the scene.
The cause of the fire is under investigation.