A 51-year-old male with a clinical history of abdominal pain and bloody diarrhea underwent spiral computed tomography of the abdomen with intravenous contrast medium enhancement. The findings were an inflammatory mass with cystic and solid characteristics arising from the ileocecal region and extending to the peritoneum and right iliopsoas muscle, with adjacent lymphadenopathy. Histology after surgical resection confirmed the diagnosis of actinomycosis lesions in perienteric fat.