An 80-year-old male was admitted to our hospital on February 16, 2009, complaining of having suffered right lower quadrant pain for a period of 4 days. Abdominal computed tomography (CT) showed a mesenterial abscess adjacent to the terminal ileum, and the possibility of acute appendicitis was excluded from the preoperative diagnosis by this imaging. Upon surgery, the appendix and cecum revealed normal appearance, without the presence of ascites. However, ileocecal resection was performed because of abscess formation that appeared to originate from the terminal ileum or the cecum. Resected specimens showed ileal diverticula, including one that was perforated. Perforation of ileal diverticula should be a candidate for the differential diagnosis of an inflammatory process near the ileocecal region.