The Lonoke County Sheriff's Office says an old but live hand grenade with an extremely rusted pin which was still intact, was found in the car's trunk wheel well.
Deputies were called to the man's home on Highway 15 North around 9:30.
The grenade was inside a plastic cup.
The man told deputies he took the item from the car and covered it with a trash can in his yard.
The Arkansas State Police Bomb Squad was called in to remove the grenade, and deputies also notified the federal Alcohol, Tobacco and Firearms agency.