Obturator hernia is relatively rare and is a diagnostic challenge in the emergency department because the hernia mass is usually concealed beneath the pectineus muscle. We report the case of a 91-year-old emaciated woman with an incarcerated obturator hernia. The hernia was discovered early in the emergency department by computed tomography and was reduced by emergency laparotomy. The Howship-Romberg sign and pain from the ipsilateral thigh to the knee are important clinical manifestations raising suspicion of obturator hernia, but these did not occur in our patient. One of the clinical clues in our patient was small-bowel obstruction of unknown origin, diagnosed by computed tomography. We emphasize that emergency physicians should keep a high index of clinical suspicion for obturator hernia when encountering small-bowel obstruction in emaciated elderly women. Although we cannot shorten the time from onset of symptoms to hospital admission, we can make rapid evaluation and surgical intervention to reduce the morbidity and mortality of obturator hernia.