A 70-year-old man complaining of fever and chills was admitted to our hospital. A computerized tomography scan revealed a bladder tumor (cT3bN0M0), and urinary cytology demonstrated neuroendocrine carcinoma. Prostate specific antigen (PSA) was 4.089 ng/ml and human cytokeratin 19 fragment (CYFRA 21-1) was 3.8 ng/ml. He underwent transurethral resection of bladder tumor and needle biopsy of the prostate. Pathological examination demonstrated small cell carcinoma in the bladder tumor specimen and well differentiated adenocarcinoma (cT1c) with a Gleason score of 34 in the prostatic specimen. He underwent cystoprostatectomy with bilateral cutaneous ureterostomy. He did not receive adjuvant chemotherapy because of the poor postoperative systemic condition and he died of acute myocardial infarction 5 months later.