Four fire engines and around 25 firefighters were called to a house fire on High Road in Willesden in Brent.
Firefighters tackled a blaze at a mid-terraced house where a significant part of the ground floor was damaged. Four people left the property before the Brigade arrived. Two men, a woman and a child suffered smoke inhalation and were treated at the scene by London Ambulance Service crews.
The Brigade was called at 0844 and the fire was under control by 0939. Fire crews from Park Royal, West Hampstead and North Kensington attended the scene.
The cause of the fire will be investigated.