We report one case of Paneth cell-like change of prostate cancer. An 81-year-old male reported to our hospital with the chief complaint of urinary retention. The serum concentration of prostate specific antigen, 168 ng/ml, was high, and digital examination was performed. Because we suspected prostate cancer, needle biopsy of the prostate was performed. Histological examination revealed moderately-poorly differentiated adenocarcinoma. Computed tomography revealed no invasion to the prostatic wall and no metastasis to the lymph node. 99mTc-HMDP revealed no bone metastasis. We chose intravenous hormonotherapy (fosfestrol 500 mg/day, 20 days), but urinary retention did not improve. Therefore, we performed transurethral prostatectomy to improve the symptoms. Histological examination of the removed specimen revealed moderately differentiated adenocarcinoma with Paneth cell-like change. Immunochemical and histochemical stains were positive for Grimelius, serotonin and prostatic acid phosphatase and negative for periodic acid-Schiff reaction, lysozyme, neuron specific enolase, prostate specific antigen, alpha-1-antitrypsin and IgA.