This is the first case report of this rare benign multiple hamartomatous tumor of the mesentery and greater omentum in Japan. The patient was an 18-month-old boy who presented with fever, abdominal distention and abdominal pain of three days duration. On admission, a mass was palpable in the lower abdomen and together with rebound tenderness and anemia. Hemorrhage from disrupted abdominal mass was suspected. An emergency laparotomy revealed a hemorrhagic solid mass (10×7×6cm) arising from mesentery of the ileum. In addition to it, multiple nodules were found in the greater omentum adherent to the tumor. Under the intraoperative diagnosis of malignant mesenterial tumor with omental metastases, the tumor including adjacent ielum and a part of the greater omentum was removed and enlarged mesenterial lymphnodes were biopsied. Histopathologically the diagnosis of omental-mesenteric myxoid hemartomas was made. The patient is free from tumor at 25 months after surgery.