A rare case of lymphangioma of the jejunal mesentery in a 34-year-old woman is presented. She was diagnosed as having an ovarian cyst preoperatively, but laparotomy revealed a cystic tumor of the mesentery that was histologically diagnosed as lymphangioma. Thus far, 44 cases of adult mesenteric lymphangioma have been reported in Japan. In nine cases, accurate diagnosis of mesenteric cysts was obtained preoperatively. In 31 cases, complete excision with or without bowel resection was done, whereas two cases were partially resected and one case was drained.