The mesenteric chylous cyst (MCC) is a rare intra-abdominal cystic disorder, and its preoperative diagnosis is difficult. A 51-year-old woman was admitted for abdominal pain and discomfort in the mesogastrium that had begun 4 weeks previously. Abdominal ultrasonography (US) and computed tomography (CT) scanning demonstrated a giant intra-abdominal cystic mass without any relation to uterus, adnexa or organs of the epigastrium. The preoperative diagnosis was a mesenteric cyst. A laparotomy showed a chylous fluid-containing cystic mass that arose from the mesentery of the upper part of the jejunum. The cystic tumor was removed without intestinal resection. Histological examination confirmed the diagnosis of a simple lymphatic cyst. The patient has been well and free of recurrence for 16 months postoperatively. The clinical management, pathological findings and a review of the literature are discussed in this report.