Three Meridian fire units responded to a call at the Mark Apartments on North Hills Street in Meridian around noon Friday.
Battalion chief Anthony Clayton said a neighbor in an adjoining apartment was awakened by a smoke detector.
The blaze was fully involved by the time firefighters were able to reach the scene.
"We ventilated it. Also we got up in the attic, knocked it out. So we kept it from spreading," said Clayton. "The fire's going to be contained to one apartment unit. There is going to be smoke and water damage to the other units, but it was hustle that stopped the fire. Hustle and training."
Clayton said the cause of the fire has not yet been determined, but has been ruled accidental. It apparently started on the patio.