A follow-up ultrasonography study 43 months after an operation for left stage I testicular seminoma in a 39-year-old man revealed left hydronephrosis. Serum beta-human chorionic gonadotropin (beta-hCG) levels were slightly increased. Computed tomography scans of the abdomen showed a bulky tumor around the ureteropelvic region without para-aortic lymph node enlargement, but did not show a clear distinction between a recurrence of the testicular tumor and an invasive ureteral tumor. After the patient underwent two cycles of chemotherapy with cisplatin and etoposide, the tumor mass decreased by approximately 60% and beta-hCG levels returned to normal. We then performed a resection of the residual tumor involving the upper ureter and left kidney and a retroperitoneal lymph node dissection under a clinical diagnosis of recurrence of the testicular tumor. Histologically, no viable cancer cells remained. The patient has been well with no evidence of recurrence for more than two years.