A 16-year-old girl was admitted to hospital with lower abdominal pain. An ultrasound examination suggested an ovarian cyst. A laparoscopic procedure found that a duplication cyst in the patient's ileum had caused mechanical ileus. The cyst was surgically resected through the creation of an end-to-end anastomosis, and pathological examination confirmed it to be a duplication cyst. Duplication cysts are a rare congenital disorder, especially past infancy. They are characterized by an epithelium of gastrointestinal origin and a lining of smooth muscle in their walls. The treatment is surgical resection when possible.