We report a case of adenocarcinoma of the urinary bladder, mimicking simple ureterocele in a 55-year-old man, presenting irritative bladder symptoms. The literature review highlights the rarity of such tumor. Intravenous urography showed. a dilated terminal portion of the left ureter resembling a cobra-head appereance. Cystoscopy revealed suspicious hyperemic lesion on the mucosa of the dilated terminal portion of the left ureter. Transurethral biopsy of the lesion was performed and pathological examination revealed a muscle-invasive adenocarcinoma. There were no metastatic lesions on computed tomography. The patient underwent radical cystectomy and urinary diversion.