A 66-year-old woman was referred to our institute for an enlarging tumor of the thyroid, and neck and chest computed tomography scan showed not only a thyroid tumor, but also an anterior mediastinal tumor and ground-glass nodules in the lung. Because of persisting symptoms, an enlarging thyroid mass, and the possibility of cancer, excision of the tumors was proposed. A 6-cm-long vertical skin incision was made in the right axilla, a mini-thoracotomy was made in the third intercostal space, and an additional port was placed in the fifth intercostal space. Thoracoscopic partial resection of the right upper lobe of the lung was performed first. Then, the da Vinci surgical system (da Vinci, Intuitive Surgical Inc., Sunnyvale, CA, USA) was introduced through the mini-thoracotomy. The mediastinal tumor was then excised circumferentially robotically. After resection of the lung and mediastinal tumors, the da Vinci was undocked, and a subcutaneous tunnel from the axillary incision to the thyroid was created using the flap dissection technique. The da Vinci was re-introduced through the axillary incision. A long camera port was used, and the skin and muscle flap was elevated to maintain adequate working space during the robot-assisted thyroidectomy. Total operating time was 277 min, and the patient’s postoperative course was uneventful. The histopathological examinations of the lung, mediastinal, and thyroid tumors were adenocarcinoma, thymolipoma, and adenomatous goiter, respectively. In conclusion, single-incision robotic surgery for three lesions was achieved safely with good clinical results and excellent cosmetic results.