Horseshoe kidney is a rare congenital anomaly showing various degrees of fusion and accessory blood supply. Coexistence of horseshoe kidney and aortic aneurysm therefore presents a technical challenge to vascular surgeons. We report an 83-year-old woman with a ruptured abdominal aortic aneurysm associated with horseshoe kidney. Preoperative computed tomography (CT) showed discontinuity of the aneurysm wall in relation to the isthmus of the horseshoe kidney, and rupture of the aneurysm into the retroperitoneal space. The aneurysm was exposed via a transperitoneal approach, and grafting was performed successfully together with division of the isthmus of the horseshoe kidney. Renal function showed no impairment postoperatively.