SummaryAlthough intussusception is a common cause of intestinal obstruction in children, intussusception of mucinous cystadenoma (MCA) of the appendix characterized by distension of the lumen due to accumulation of the mucoid substance is rarely reported. Diagnosis of MCA is usually made perioperatively. In these cases, as a general approach, an appendectomy is performed for cystadenoma, and right hemi-colectomy is recommended for cystadenocarcinoma. However, the type of surgical treatment is related to the dimensions and histology of the lesions. A 12-year-old boy was admitted to our clinic with symptoms of a mobile and painful mass in the right upper quadrant of the abdomen. Abdominal ultrasonography showed intussusception as well as a large, cystic and solid structure extending from cecum to transverse colon. Reduction of intussusception and right hemi-colectomy were performed subsequent to laparotomy. Pathologic diagnosis was reported as MCA. Although MCA is seen rarely, it always should be kept in mind in differential diagnosis of intussusception and intra abdominal mass, especially in children with abdominal pain and distension.