Four fire engines and around 25 firefighters tackled a fire at a house on Headstone Road in Harrow.
Part of the first floor was damaged by fire. One woman was taken to hospital by London Ambulance Service crews.
The Brigade was called at 1512 and the fire was under control by 1636. Firefighters from Stanmore and Wembley fire stations attended the scene.
The cause of the fire is under investigation.