Duplication cysts are rare gastrointestinal congenital abnormalities of the GIT. Completely isolated duplication cysts are extremely rare. Herein we report a case of non-communicating isolated duplication cyst which was clinically, radiologically and at surgery (peroperatively) mimicking ovarian cyst. A one day old female child presented with abdominal distension and a palpable abdominal mass. USG of the abdomen suggested a differential diagnosis of duplication cyst, mesenteric cyst or ovarian cyst. At surgery cyst was seen adherent to the right ovary. Histopathological examination revealed non communicating duplication cyst.