Aneurysms of the superior mesenteric artery branches are rare. Spontaneous intra-abdominal hemorrhage resulting from rupture of a visceral artery aneurysm is difficult to diagnose and carries high mortality. We present a case in which a rupture of the right colic artery aneurysm presented as an acute abdomen. Diagnosis was established intraoperatively. Angiography and a high degree of suspicion are valuable diagnostic tools. Exact etiology was not determined in our case. Because of high risk of rupture, aneurysms of the superior mesenteric artery branches should be resected.