We report a case of a patient with a fistula between the left ureter and abdominal aorta. The patient was a 44-year-old male who had undergone radiation therapy (intraoperative: 25 Gy, external beam: 50 Gy) and chemotherapy (CDDP: 250 mg) for retroperitoneal lymph node metastasis from seminoma. His postoperative course was complicated by stenosis of bilateral ureters, which were treated by indwelling double J-stents. Fifteen years after the operation, gross hematuria occurred from the left ureteral orifice when exchanging the left ureteral double J-stent. Computed tomographic scan demonstrated left ureteral-abdominal aortic fistula formation at the crossing point. Massive hemorrhage was suspected to have prompt fistula formation between the left ureter and the aorta. At exploration, there was a fistula of about 7 mm in diameter at the anterior surface of the aorta, and the stent was presumably inserted from it. The aortic fistula was successfully closed. In addition, the left ureter was ligated proximal to the fistula and percutaneous left nephrostomy were performed. His postoperative course was uneventful. We should be aware that uretero-arterial fistula can occur as a serious complication of ureteral catheter exchange after prolonged ureteral stenting and radiation therapy.