Six fire engines and around 40 firefighters were called to disused train carriages alight next to Southall train station.
One derelict train carriage was destroyed by the fire and a further two were damaged. There were no reports of any injuries.
The Brigade was called at 0225 and the fire was under control by 0553. Fire crews from Southall, Heston, Ealing and Hayes fire stations attended the scene.
The cause of the fire is under investigation.