Spontaneous retroperitoneal hematoma after warfarin therapy is an extremely rare event. Here, we report a 25-year-old man who was brought in to the emergency service with confusion. On arrival, the patient had hypotension, tachycardia, tachypnea, low-grade fever, and Glasgow Coma Scale score of 12. Abdominal examination revealed distention and mild tenderness in the right upper quadrant of the abdomen. The patient had a history of aortic valve replacement surgery and was on warfarin treatment at an international normalized ratio of 2.4. Our patient progressed to cardiorespiratory arrest. The resuscitation was initiated promptly. Despite all resuscitation measures, including transfusion and administration of high doses of catecholamine, the patient died of hypovolemic shock 3 hours after admission. At autopsy, the external surface of the abdominal great vessels (descending aorta and mesenteric vessels) showed scattered petechial hemorrhages without any visible site of perforation. After comprehensive exploration of the abdomen, no evidence of traumatic event was identified and the cause of internal blood loss was noted as warfarin adverse effect.