We present a case of haemoperitoneum in a child, who presented with signs of acute abdomen with subacute intestinal obstruction. Abdominal paracentesis aspirated fresh blood. Ultrasound and CT scan abdomen showed loculated haemoperitoneum. A definitive diagnosis could not be made andan exploratory laparotomy was undertaken which revealed a large cystic lymphangioma of greater omentum with acute massive spontaneous haemorrhage. It was excised in toto along with the involved omentum leading to excellent recovery. Abdominal cystic lymphangioma first presenting as a spontaneous, life threatening haemorrhage has to our knowledge, not been reported before. It may have to be included in the differential diagnosis of acute haemoperitoneum.