A 67-year-old man was admitted to the hospital because of increasing right lower abdominal pain and fever elevation. On physical examination a tumor was palpated in the right lower abdomen. It was associated with redness and tenderness, and muscle guarding was present. Laboratory data showed the existence of severe inflammation. CT and echogram revealed intra-abdominal abscess close to the abdominal wall. Then drainage was performed. Irrigography showed multiple diverticula of the appendix, cecum and ascending colon. Tip of one of the appendiceal diverticula was communicated to the abscess cavity. Ileocecal resection was performed for abscess formation due to perforation of the appendix. Histological diagnosis was pseudo-diverticula of the appendix and cecum. Surgical treatment including prophylactic appendectomy would be necessary especially for the aged with appendiceal diverticula because of the high risk of perforation and abscess formation.