Four fire engines and around 25 firefighters were called to a fire at a flat on Winslow Close in Neasden.
Half of a ground floor flat in a three-storey block was damaged by the fire. Two adults and four children left the property before the Brigade arrived. One woman was treated on scene by London Ambulance Service crews.
The Brigade was called at 1615 and the fire was under control by 1722. Fire crews from Willesden, Wembley, Stanmore and West Hampstead fire stations were at the scene.