Intussusception is a frequent cause of bowel obstruction in the first five years of life and it is one of the most common surgical emergencies in infancy and early childhood. The age of five months child was administered in Department of Pediatrics of Chunchon Sacred Heart Hospital. His main symptoms were vomiting and high fever for three days. Abdominal sonography, air reduction and abdominal computerized tomography (CT) were performed and the conclusion of these study was intussusception due to cyst mass lesion; duplication cyst, mesenteric cyst or Meckel's diverticulum. He was transferred for operation. We had performed laparotomy for reduction of the intussusception. Operative findings revealed ileocolic type of intussusception due to cystic tumor on ileocecal valve that was invaginated into the cecum, and hyperplasia of the Peyer's patch were seen. But we failed manual reduction because of the tumor in the ileocecal area. So we had performed partial resection of the ileocecum. Diverticulum of the ileum was confirmed by pathologic examination. We experienced unusual cause of the intussusception. So we report this case with a review of the literatures.