The shooting happened at about 2 p.m. at La Marina Mariscos restaurant, located at 1261 E. Algonquin Road, Des Plaines police said.
A man allegedly entered the restaurant looking for someone, however that person exited a different door.
Police said the two men then confronted each other in the parking lot and started to shoot at each other.
No injuries were reported, according to police.
Both men got away, one ran on foot while the other drove off in a blue pick-up truck, Des Plaines police said.
Officers found eight shell casings, six .40 caliber casings and two 9mm casings. Officers also recovered a loaded .40 caliber handgun in the rear of the business near a dumpster.
Police said there is no threat to the public.
Anyone with information is asked to call police.