This case report presents a rare anatomical variation known as double ureter, where a comprehensive unilateral duplication of the left ureter originating from a single renal tissue was incidentally discovered during staging laparotomy for CA endometrium. This congenital anomaly significantly heightens the possibility of unintentional damage to the ureter during surgeries involving the pelvic area. In summary, ensuring careful exposure of both ureters along with the continuous vigilance of surgeons remains pivotal for ensuring a secure surgical procedure.