Crews responded to the scene, in the 200 block of Taylor Avenue NW, at about 2 a.m. after receiving a report of smoke and flames at the Ukrainian Christian Church.
When firefighters arrived, flames had reached into the eaves and attic of the building, and crews had to cut holes in the roof to fight the blaze.
The arson caused some $750,000 to $1 million in damage, said Ted Hickey, Renton Fire Department investigator.
"There's a lot of extensive damage in the roof structure itself," he said.
Church Administrator Vitaliy Soltys said the arson and the damage it caused are "unbelievable." She said the church has never had any problems with anyone before this.
Investigators believe the fire was started in a debris pile outside of the auditorium.
No suspects have been identified, he said, adding that the arson does not appear to be a hate crime. "There is some graffiti around but that is pretty common just about everywhere," Hickey said.
No one was in side the church at the time of the fire, and there were no injuries. The church auditorium sustained major water damage from the firefighting efforts.
Renton fire investigators say this is the sixth fire they've investigated in the past couple of weeks where flammable material outside the building may have been lit on fire.
The federal Bureau of Alcohol, Tobacco, Firearms and Explosives has been called in to assist with the investigation.