Four fire engines and around 25 firefighters were called to a house fire on North Circular Road in Neasden.
Most of the ground floor of the end of terrace house was destroyed by the fire. There were no reports of any injuries.
The Brigade’s fire investigators believe the blaze was accidental and caused by the unsafe disposal of smoking materials.
A London Fire Brigade spokesperson said: “A London Fire Brigade spokesperson said: "We'd rather you didn't smoke at all, but if you are a smoker it's absolutely vital you ensure your cigarette is completely out when you've finished smoking it.
"If you don't, you risk causing a fire which could not only destroy your home but also cost you your life."
The Brigade was called at 0021 and the fire was under control by 0124. Fire crews from Wembley, North Kensington, Hendon and Willesden fire stations were at the scene.
Safety advice for smokers