A 28-year-old man with no previous history of abdominal surgery presented at a local hospital with abdominal pain. He was diagnosed to have an intestinal obstruction and was treated conservatively. However, the symptoms persisted, and he was thereafter referred to this hospital. Plain abdominal radiographs demonstrated small-bowel gas. A computed tomographic scan of the abdomen disclosed wall thickening of an edematous, fluid-filled ileum. An exploratory laparotomy was performed to determine the cause of the intestinal obstruction. The ileum had herniated into the intersigmoid fossa, 100 cm proximal to the ileocecal valve, and the patient was diagnosed to have an intersigmoid hernia. Since the incarcerated portion of the small bowel was viable, reduction of the hernia and closure of the defect in the sigmoid mesocolon were performed. The postoperative course was uneventful. A sigmoid mesocolon hernia is an uncommon condition. This report presents a case of intersigmoid hernia and a review of 60 cases of sigmoid mesocolon hernia reported in Japan.