RATIONALE: Although percutaneous endoscopic gastrojejunostomy (PEG-J) tubes are believed to reduce the side effect of aspiration, cautious catheter management is required. Intussusception is a serious complication of these tubes. PATIENT CONCERNS: A 7-year-old boy bedridden with hypoxic encephalopathy owing to drowning at the age of 1 year was admitted our hospital with urinary retention for 1 month. At the age of 4 years, a PEG-J tube was inserted. Concomitant with hyperaldosteronemia, an intestinal intussusception from the duodenum to the jejunum was observed via computed tomography (CT). The patient's condition worsened dramatically; gastrointestinal perforation was suspected, and laparotomy was performed. DIAGNOSIS: Jejuno-jejunal intussusception. INTERVENTIONS: Open surgery was performed to release the intussusception. By assessing the reduced intestinal tract, the intussusception starting from a 50 cm portion from the Treitz ligament had been extended to 100 cm from the Treitz ligament. The oral side jejunum was dilated. No evidence of intestinal perforation or strangulated ileus was observed, and the intussusception was manually remediable. OUTCOMES: Preoperative CT examination showed intussusception from the duodenum to the jejunum. Laparotomy showed intussusception on the anal side of the Treitz ligament. With regard to the CT findings associated with the progression of intussusception to the duodenal site, as a result of the telescope phenomenon extending to the duodenum due to the relaxation of the Treitz ligament through repeated intussusception, it was considered that CT examination revealed intussusception extending from the jejunum to the duodenum of oral side. After 3 postoperative weeks, the patient was finally able to return home. LESSONS: If the ileus is observed during the insertion of a PEG-J, clinicians should consider the possibility of intussusception even in the duodenum.