A 71-year old male visited our hospital with a chief complaint of pollakisuria. The needle biopsies of the prostate were performed with PSA 8.0 ng/ml, and he was diagnosed as moderately differentiated adenocarcinoma. Imaging techniques revealed a right complete duplicated upper urinary system with an ectopic ureter draining to the prostatic urethra. He received radical prostatectomy with concomitant anastomosis of ureter to ureter. There is no evidence of hydronephrosis or tumor recurrence 11 months after operation. This is, to our knowledge, the second case report describing the association of radical prostatectomy and ectopic ureter.