Fire fighters were called to Allen Kia Bath on Lower Bristol Road in Twerton, during the early hours of this morning.
Three crews from Bath and one from Brislington attended the incident at 3.40am, where four vehicles were ablaze.
There was also severe damage to the exterior walls and windows of the showroom.
According to the Bath Chronicle, the cause of the fire remains unknown.
Police and fire officers are due to examine the scene today.