Objective: Unusual clinical courseBackground: Endometriosis is a disease characterized by endometrial tissue appearing outside the uterus, mainly involving the peritoneum and pelvic organs. Ureteral endometriosis (UE) is rare, typified by deep infiltrating endometri-osis involving the ureter and can result in ureteral obstruction, proximal hydroureter, hydronephrosis, and im-pairment of renal function. Symptoms may be insidious and nonspecific and may lead to a prolonged disease course. We describe a patient with UE complicated by hydronephrosis.Case Report: A 42-year-old woman was admitted to the Urology Department with the incidental discovery of right hydrone-phrosis. After a thorough examination, she underwent right ureteral mass resection and right ureteral stump anastomosis. The pathology report indicated endometriosis. The patient was given 6 doses of gonadotropin-releasing hormone agonist immediately after surgery, followed by an intrauterine levonorgestrel-releasing sys-tem. Postoperative follow-up showed that no recurrence was observed in this year. Here, we briefly summa-rize the epidemiology, pathogenesis, clinical presentation, imaging, treatment, and prognosis of the disease.Conclusions: UE should be listed as one of the differential diagnoses of unexplained hydronephrosis in women of childbear-ing age, and those with dysmenorrhea should be cognizant of this disease. Active surgical treatment and long-term management should be carried out to obtain better prognosis.