Peritoneal encapsulation (PE) is a rare anatomic anomaly which occurs due to an accessory peritoneal sac covering the small bowel which can cause chronic recurrent abdominal pain and even small bowel obstruction, most often in children or patients with no previous surgical history. The diagnosis is usually made during surgery, but recently it has been suggested that mindful examination of the abdominal CT may be helpful in considering PE beforehand. We present the case of a 21-year old patient who was admitted due to intense abdominal pain, asymmetrical abdominal distension, air fluid levels on the abdominal X-ray, but no specific findings on the abdominal CT. He underwent emergency surgery and PE was found and the peritoneal sac was excised. The postoperative course was uneventful. Histopathologic examination of the specimen confirmed the diagnosis. PE is often misdiagnosed as abdominal cocoon or sclerosing encapsulating peritonitis, but it is a pathology with a much lower rate of recurrence and postoperative complications, which can be treated successfully if the surgeon is aware of this pathology when making the differential diagnosis.