A 9-year-old boy presented to our clinic with fever, nausea, vomiting, and colic pain on his left side. Physical examination revealed sensitivity in the costovertebral angle and ureteral points. Urinalysis indicated macroscopic hematuria. The results of the biochemical examination were normal; however, ultrasonography (USG) revealed grade 2 dilatation in the pelvicalyceal system of the left kidney. The patient was suspected with ureteric stone, and a direct urinary system graph was obtained during pain control with analgesia. However, this did not reveal any stone formation. Therefore, magnetic resonance urography was performed; this revealed a filling defect in the left proximal ureter (), which was clinically and radiologically considered to be an urothelial carcinoma. Cystoureteroscopy was performed. A pedunculated polyp from the orifice to the UPJ was detected, and the stalk of the polyp was separated from the ureter wall using a Ho: YAG laser (). Subsequently, the entire tissue (10 cm) was removed with forceps (). There were no postoperative complications, and the patient was discharged on the first postoperative day. Laboratory tests performed during the first postoperative week were normal. USG revealed no sign of ectasia in the left kidney. Histopathologic examination of the polyp under a microscope revealed edema covered by fibrovascular stromal tissue and a fibroepithelial structure composed of normal transitional epithelium with distinctive vascularization (). Written informed consent was obtained from the patient's parents.