BACKGROUND Segmental arterial mediolysis (SAM) is not yet well known in the neurosurgical field, even though it has become an increasingly recognized pathology in arterial dissection. CASE DESCRIPTION A case of SAM presented as subarachnoid hemorrhage (SAH) due to a dissecting aneurysm of the left intracranial vertebral artery (VA), which extended from the proximal VA union to the distal portion of the left posterior inferior cerebellar artery. The lesion was successfully embolized by an endovascular technique. However, subsequent intraperitoneal hemorrhage due to rupture of a fusiform aneurysm of the middle colic artery prompted surgical treatments. The features of the extirpated visceral vascular lesion were compatible with the diagnosis of SAM based on histopathologic examinations. CONCLUSIONS It is very important that SAM is recognized as a systemic disease that affects the central nervous system, visceral arteries, and coronary arteries. The possibility of SAM should always be considered, particularly in patients with ruptured VA dissection-which is nowadays treated by endovascular techniques-since concomitantly involved visceral arteries may cause unexpected hemorrhagic complications other than SAH.