A case of bilateral obturator hernias which was diagnosed by ultrasonography (US) and computed tomography (CT), and repaired by a retropubic extraperitoneal operative approach under spinal anesthesia is reported herein. A 91-year-old woman presented with lower abdominal and left groin pain consistent with a Howship-Romberg sign. US demonstrated an image of the bowel projecting from the small pelvic space to the left thigh with a to-and-fro movement of the bowel contents. The definitive diagnosis of an incarcerated left obturator hernia was made by CT which also revealed a mass in the right obturator foramen. Surgery was performed through a retropubic extraperitoneal approach under spinal anesthesia. No necrosis was observed in the incarcerated bowel and resection was not necessary. A simple hernial sac was found in the right obturator canal. The operation using the retropubic extraperitoneal approach was successful and we believe it to be the most effective procedure for obturator hernias which have been diagnosed early.