We performed robot (da Vinci)-assisted thoracoscopic extended thymectomy (rThx) for myasthenia gravis with thymoma. The patient was a 66-year-old woman who complained of palpebral heaviness. Robotic operation was performed in the supine position by placing four ports in the right chest wall under 10 mmHg CO(2) insufflation using three arms and one assist port. Compared with conventional video-assisted thoracic surgery (VATS), the bilateral upper horns, fat around the diaphragm, and aortopulmonary window could be resected more easily. The tumor measured 41 mm maximum diameter and was diagnosed as type AB noninvasive thymoma. The operating time was 298 min, console operating time was 203 min, and the amount of bleeding was small. The postoperative course was uneventful with no complications. This is a report of the first Japanese case of rThx for myasthenia gravis. rThx is a promising technique, and further improvement in the procedure is expected.