Mesocolic hernias are rare congenital anormalies resulting from abnormalities in the intestinal rotation during embryonic development, and comprise approximately 53% of all congenital internal hernias. A right mesocolic hernia is formed by the arrest of further rotation of the prearterial segment of gut in the right side of the abdomen, with continued rotation of the postarterial segment, during the second stage of embryonic intestinal rotation, leading to the entrapment of almost the entire small bowel behind the right colonic mesentery. The condition may be discovered incidentally during at laparotomy, or may be the cause of an acute small bowel obstruction. Cecal diverticulitis is a rare disease, whose symptoms are similar to acute appendicitis. It is difficult to diagnose the two diseases accurately prior to operation. We report on a 48-year old man, who had perforated cecal diverticulitis and an incidental right mesocolic hernia, with a review of the literature.