The patient, an 81-year-old woman, had the chief complaint of macroscopic hematuria. Cystoscopy revealed a bladder tumor, which was determined by biopsy to be mucin-producing adenocarcinoma. Appendiceal carcinoma that invaded the bladder were diagnosed preoperatively by air-contract barium enema and magnetic resonance. She was treated with partial cystectomy and resection of the cecum. Sixteen cases of appendiceal carcinoma with invasion into the bladder have been reported in Japan.