Boise Fire crews have contained a fire at the Gene Harris Bandshell in Julia Davis Park.
An investigation is now underway to determine a cause.
Boise Fire says the call came in at 8:15 p.m.
A spokesman says the flames started on the exterior of the building, before spreading up the wall and into the attic space.
Boise Fire says no one was injured. The roof, which is now weakened, is weighed down by heavy tiles.