The incidence of an ectopic ureter in male patients is low. The ectopic ureter in men often ends at the seminal tract in association with renal dysgenesis. Malignant transformation of this closed, nonfunctional urothelial system has been reported only once. To our knowledge, we report the first case of primary transitional cell carcinoma in a single ectopic ureter with a dysplastic kidney that terminated in the ejaculatory duct.