Internal hernia is an unusual cause of intestinal obstruction, and the through sites of hernias may include the paraduodenum, transmesenteric region, foramen of Winslow, paracecum, the broad ligament of the uterus, and the transomental region. Transomental hernia is the rarest type of internal hernia and accounts for fewer than 1% of internal hernias. Transmesenteric and transomental hernias are different from the other types of internal hernia, and usually present acute intestinal obstruction with strangulation of the small bowel. We report a 74-year-old male with initial manifestation of peritonitis. Internal hernia-induced intestinal obstruction with strangulation was highly suspected from the image study. After an urgent exploratory laparotomy, transomental hernia was diagnosed.