The incident happened at the Walsall branch of the Mountain of Fire and Miracles Ministries, in Town Hill, at about 11.20am on Sunday.
Emergency crews arrived to find smoke in the basement at the place of worship off Upper Rushall Street in the town centre.
Church leader Pastor Tony Adams said: "There was no real damage as such. It wasn't a serious fire. We're cleaning up the premises now.
"The incident involved one room. We're not sure what caused it."
A West Midlands Fire Service spokeswoman said: "Nobody was trapped or injured. Crews are having trouble with fire doors being locked and they are trying to get through.
"They are just using cutting apparatus to remove shutter doors and allow ventilation. We don't know what has caused it."
Walsall and Bloxwich fire stations sent crews to the fire and used a hose reel jet and ventilation fans to tackle the blaze on December 26.
Walsall Fire Station shared pictures on social media and said: "Green Watch in attendance at a fire at a local place of worship, crews have used one hose reel jet and positive pressure ventilation to deal with this incident."
The Mountain of Fire and Miracles Ministries is a Pentecostal church founded in Nigeria in 1989 by Daniel Kolawole Olukoya and now has branches across the world.
The owner of the building, a former restaurant, has also visited the site.