Primary large cell neuroendocrine carcinomas (LCNEC) of the urinary bladder are rare. Reported herein is a case of a primary, pure LCNEC occurring in a man. The patient was a 32-year-old man who presented with hematuria of 1 week's duration. On cystoscopic examination, a solitary mass measuring 3 cm in diameter was detected protruding from the anterosuperior wall of the urinary bladder. Two months after the primary transurethral resection, significant regrowth of the remnant mass was noted on CT, and the patient underwent a partial cystectomy. A diagnosis of LCNEC was made based upon histological and immunohistochemical findings. Tumor cells were positive for synaptophysin, chromogranin A, CD56, epithelial membrane antigen, and cytokeratin. Histologically, the tumor penetrated the deep muscle and perivesical fat. In spite of three cycles of chemotherapy, the patient developed multiple metastases in the lung and liver 10 months postoperatively. LCNEC of the urinary bladder are uncommon entities, which have a possible fatal outcome.