A 67-year-old female with abdominal pain and vomiting was admitted to our hospital. Abdominal X-ray showed dilated small bowel in the left upper abdomen. She was diagnosed with ileocecal intussusception based on abdominal contrastenhanced computed tomography. Computed tomography showed a "pseudo kidney sign" in the right flank region. We also observed an enhanced mass lesion in the presenting portion ofthe intussusception. Laparotomy was performed to treat the invagination. We tried to reduce the invagination, without success. Ileocecal resection was performed. Pathological findings revealed that poorly differentiated adenocarcinoma in the ileum end portion had induced the invagination. Intussusception in adults should be treated with the knowledge that about 80% ofsuch cases have an organic lesion in the presenting portion.