A 75-year-old man visited our hospital complaining of a foul smelling, painful swelling of the glans of the penis. Physical examination showed a true phimosis and a huge solid mass on the glans under the foreskin. After postectomy and penile tumor biopsy, we performed partial penectomy. Histologically, the tumor was composed of atypical spindle cells arranged in an epithelioid pattern and stained positive for both epithelial and mesenchymal markers. Therefore we diagnosed the tumor as sarcomatoid carcinoma of the penis. One month after surgery, advanced gastric cancer was discovered. Thereafter, cancer rapidly spread throughout the whole body, and he died six months postoperatively.