Abdominal apoplexy is a clinical entity characterized by spontaneous intraperitoneal hemorrhage from rupture of a visceral vessel. We describe a 34-year-old man who presented with abdominal apoplexy due to rupture of an ileocolic aneurysm. Subsequent biochemical and genetic analysis confirmed the diagnosis of Ehlers-Danlos syndrome type IV based on abnormal production of type III procollagen and a novel mutation in the COL3A1 gene. Patients presenting with abdominal apoplexy should undergo a thorough examination so that the underlying vascular pathology can be identified.