Intussusception typically occurs in childhood, presenting with a well-known medical history and clinical symptoms. Pathologically, a "leading point" may be attributed to lymphadenomatosis, polyps, or a tumour. In older patients and adolescents, the diagnosis can be complicated due to the lower incidence and variable subacute symptoms. We report on an 18-year-old patient with increasing abdominal discomfort over several weeks. External diagnostics showed no pathological signs or were misinterpreted as a malfunction of intestinal motility. The patient experienced increasing colics, recurrent vomiting, dehydration and weight loss. Finally he was transferred to our paediatric surgical department and laparotomy had to be performed for the clinical and radiological signs of an ileus. An ileoilealic intussusception was found, caused by a small bowel tumour, which almost completely obstructed the intestinal lumen. It was resected and bowel continuity was re-established. Histopathology revealed a very rare, highly malignant mesenchymal Ewing sarcoma, infiltrating the complete bowel wall. After the postoperative course, the patient was transferred to our oncological department for chemotherapy. In older children or young adults, intestinal malignancies are extremely rare. Nevertheless, if these patients suffer from unspecific complaints of chronic intestinal obstruction, a tumour must be ruled out. A Ewing sarcoma may be responsible for an intussusception.