Four fire engines and around 25 firefighters were called to a flat fire on Handley Grove in Cricklewood.
A flat on the second floor of a three-storey block was damaged by the fire. Two people left the property before the Brigade arrived. They were treated on scene by London Ambulance Service crews. Another four people were led to safety from the building by firefighters.
The Brigade was called at 0102 and the fire was under control by 0216. Fire crews from West Hampstead, Willesden and Hendon fire stations were at the scene.
The cause of the fire has been recorded as undetermined.