Our aim was to define clinical long-term outcome of surgery for neurogenic thoracic outlet syndrome without rib resection, and to find factors predicting long-term results. For the 94 patients, the main outcomes were pain, numbness, weakness, and upper-extremity function. The Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) survey, the Cervical-Brachial Symptom Questionnaire (CBSQ), and a numerical rating system served as functional outcome measures. Mean follow-up was 12.9 years. Preoperative pain diminished from 7.8 to 2.2, numbness from 7.4 to 4.0, and weakness from 7.3 to 3.8. Grip strength increased from 25.7 to 31.8 kg. QuickDASH averaged at follow-up 37.1 and CBSQ 51.5. No correlation appeared between smoking and long-term results regarding pain, numbness, weakness, or functioning. Positive TOS provocative tests or intraoperative anatomical findings like consistency of the scaleni muscles showed no correlation with outcome. 82% of female and 57% of male patients reported that aid from this surgery had been excellent or good; 69% reported that surgery helped considerably for at least a mean 9.9 years. The risk for worse self-reported long-term outcome was higher among men, but neither BMI nor age at surgery associated with self-reported outcome. Pain, numbness, and weakness significantly decreased and function improved after supraclavicular release without rib resection. We found no significant preoperative nor per-operative factors predicting long-term results.