Firefighters were called to a house fire on Avenue Road in North Finchley.
A bedroom on the first floor of a terraced house was destroyed by fire. Two people left the building before the Brigade arrived and a woman was taken to hospital by London Ambulance Service crews.
The Brigade was called at 1402 and the fire was under control by 1438. Two fire engines from Barnet and Finchley fire stations attended the scene.
The fire is believed to have involved a portable electric cooker.