The fire began at about 9:30 a.m. at the restaurant on Concord Pike in Talleyville.
It was not yet known what started the fire.
A 30-year-old woman was treated for chest pain and was taken to Christiana Care Hospital for evaluation.
A 25-year-old man was checked out at the scene, but did not go to a hospital.
Video from the scene showed the flames coming through the roof of the building.
Officials closed Concord Pike in both directions while they fought the fire.