An extremely rare case of seminal vesicle cyst associated with ipsilateral renal dysplasia and ectopic ureter is presented. A 36-year-old patient underwent nephroureterovesiculectomy. Considering the clinical and imaging profile of the patient, a diagnosis of ureterocele with megaureter was initially suspected, but intraoperative findings and definitive pathological analysis of the specimen revealed right renal dysplasia with ectopic ureter opening into seminal vesicle cyst. The clinical and therapeutic peculiarities of this rare condition are presented and the literature on this topic is reviewed.