Fifteen fire engines and around 100 firefighters were called to a fire at a temple on Clifton Road in Southall.
Most of the roof and half of the first floor of the building were damaged by the fire. Part of the ground floor was also damaged. There were no reports of any injuries.
Station Commander Sami Goldbrom, who was at the scene, said: "Firefighters tackled a significant fire which took hold of the roof of the building.
“Multiple breathing apparatus crews worked hard to fight the fire internally and bring the blaze under control. A turntable ladder was used for observation.
“Firefighters also carried out damage control to salvage any valuable items not affected by the fire.
"There was residential accommodation at the rear of the building, but there were no reports of any people being involved.
"This was in a very busy part of Southall so there was a lot of traffic and motorists were advised to avoid the area where possible."
The Brigade was called at 1229 and the fire was under control by 1632. Fire crews from Southall, Hayes, Hillingdon and Heston fire stations were at the scene.
The fire is believed to have been accidental and due to an electrical fault.