Transmesenteric hernia, a type of internal hernias, is a rare cause of intestinal obstruction. This intraperitoneal hernia has no sac and is formed by protrusion of a loop of bowel through an aperture in the mesentery. Incarceration leads to intestinal obstruction and subsequently, strangulation and gangrene of varing lengths of intestine. This is a case report of 4-year-old girl with transmesenteric herniation of the terminal ileum through a defect in its own mesentery. Strangulation of the affected bowel necessitates resection and primary anastomosis with repair of mesenteric defect. The postoperative course was uneventful. Acute intestinal obstruction in the absence of an external hernia and with no history of a previous surgical procedure suggests the possibility of an internal hernia, especially if the patient has a history of chronic intermittent abdominal distress.