Segmental mediolytic arteritis is a very rare vascular disease which causes sudden intraabdominal hemorrhage. The disease is characterized by degeneration of the arterial media, followed by aneurysmal dilatation and rupture of the involved artery. Up to now, only 13 cases have been reported, and this unique disease is not fully recognized among general pathologists and physicians. Here, we present a case of segmental mediolytic arteritis involving the propria hepatic artery, which resulted in intraabdominal hemorrhage, and consequently hypovolemic circulatory disturbance. Histologically, the rupture focus showed degeneration and desquamation of the intima and media with fibrin-like material covering the exposed adventitia. Inflammatory infiltrates were only noted in the rupture focus as a secondary reactive change. Other than the rupture focus, there were two foci showing similar findings. This disease has rarely been reported and is seldom recognized as a cause of arterial rupture. In cases of sudden intraabdominal hemorrhage, segmental mediolytic arteritis should be considered as a possible cause in addition to atherosclerotic and mycotic aneurysm, traumatic injury and vasculitis syndromes.