Aim: Mesenteric cysts are rare abdominal masses which cause vomiting and distention and may be complicated with volvulus, bleeding, torsion and rupture, gastrointestinal perforation and even urinary obstruction. We present a patient with a mesenteric cyst causing gastrointestinal obstruction which treated surgically. Case: A 3 years old male patient was admitted to our hospital with symptoms of vomiting, constipation and abdominal distention. Plain abdominal anteroposterior X-ray study showed air-fluid levels and abdominal ultrasonography revealed a cystic mass of 15 × 8 cms. Abdominal computerized tomographic examination with and without contrast material revealed a giant cystic mass with septations together with secondary findings of intestinal obstruction. Exploratory laparotomy via midline incision was made. A cystic mass containing a clear fluid was observed. The mass was obstructing the ileal passage. The cyst together with 10 cms. of ileum were removed and an ileo-ileostomy was made. Pathological examination was consistent with mesenteric cyst. He was discharged to full recovery with a symptom-free postoperative tenth day. The child is doing well at 1 year after surgery. Discussion: Mesenteric cysts, although they are rare, can be easily diagnosed modern diagnostic imaging methods and treated surgically.