Four fire engines and around 25 firefighters were called to a fire in Sudbury Heights Avenue, Greenford.
A single storey garage was damaged by fire, as well as part of the roof an adjoining end-of-terrace house. There were no reports of any injuries.
The Brigade was called at 1522 and the fire was under control by 1639. Fire crews from Wembley, Northolt, and Park Royal stations were at the scene.
The cause of the fire is believed to be the unsafe disposal of smoking materials.
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.
"This is also a reminder to never try to tackle a fire yourself. Leave it to the professionals and call 999 as soon as you become aware of a fire in your home."