Leiomyomas rarely develop in the deep soft tissues except in the uterus and the gastrointestinal tract. Leiomyomas are found chiefly in adults and rarely found in children. In this paper, a child with multiple leiomyomas of the omentum and the mesentery is reported. A 6-year-old boy was admitted to our hospital with symptoms of abdominal pain and nausea following blunt trauma. Abdominal ultrasonography and CT scan revealed a solid mass in the right upper quadrant of the abdomen. An upper GI series showed two filling defects in the duodenum. Superior mesenteric arteriography revealed arterial stretching and neovascularization in the peripheral area of the gastroduodenal artery. The preoperative diagnosis was an omental neoplasm such as leiomyoma or leiomyosarcoma. At surgery, six solid tumors ranging 1 to 5 cm in diameter were located in the omentum and the mesentery. All of the tumors could be easily removed from their attachments. Microscopic exanimation confirmed the diagnosis of multiple leiomyomas. His postoperative course has been uneventful without evidence of recurrence four years after surgery.