The present study included 27 consecutive patients (30 limbs) undergoing arthroscopy-assisted transaxillary first rib resection and brachial plexus neurolysis for thoracic outlet syndrome (TOS). To improve visualization, we changed the intraoperative limb position in three stages. We assessed the intraoperative parameters, including the scalene interval width between the anterior and middle interscalene muscles (interscalene base), blood loss, operation time, preoperative and postoperative QuickDASH, patient satisfaction, and complications. The mean intraoperatively measured interscalene base width was 6.2 mm. Appropriate visualization could be obtained at zero-position in the late phase. Intraoperative blood loss and operation time were significantly less in the late phase (p < 0.001). The QuickDASH score was significantly improved (42 before surgery vs. 9 at final follow-up, p < 0.001), especially in athletes relative to non-athletes (0.2 vs 14, p < 0.001). The outcome was excellent in 43.3% of cases, good in 43.3%, fair in 13.3%, and poor in none. The present approach achieved complete relief in 43% of cases overall (91% in athletes and 16% in non-athletes). Pneumothorax was present at the early phase in 3.3%. There were no other complications and no recurrences. Arthroscopic surgery is useful for TOS, especially in athletes.