In Japan, robot-assisted thoracic surgery (RATS) was introduced in thoracic surgery in 2001, but it did not become widespread. However, surgery for mediastinal tumors and lobectomy for lung cancer with RATS were covered by insurance in 2018 and are currently becoming popular as a general practice, following video-assisted thoracic surgery(VATS). Forty-six patients with mediastinal tumors were treated by RATS from February 2014 to November 2022 in our institution. Theoretically, the RATS approach is performed from one side in a semi-supine position under CO2 insufflation as with the VATS approach of our institution. In the case of extended thymectomy, a bilateral approach is performed by changing the patient's position. The median surgery time was 88 min, and the median surgery time in unilateral and bilateral approaches were 79 and 208 min, respectively. Blood loss during surgery was quite minimum, and no patients required conversion to VATS or thoracotomy. Regarding adverse events, postoperative bleeding was observed in one patient (2.2%). RATS has been successfully introduced and expanded safely for mediastinal tumors. Considering further expansion of RATS indications while conducting verification by comparison with VATS in the future is necessary.