Background: A pectoralis major (PM) transfer is a viable treatment option for patients with scapular winging due to long thoracic nerve (LTN) palsy not responding to nonsurgical management. However, the long-term outcomes remain unknown. Therefore, the purpose of this study was to evaluate the long-term outcome of shoulder function (ie, minimum follow-up of 10 years) and quality-of-life (QoL) of patients treated for scapular winging due to LTN palsy with a PM transfer. Methods: This observational cohort study included 15 patients (16 shoulders) who underwent PM transfer, using a tendoachilles allograft, between 1995 and 2012. Shoulder forward flexion and abduction were analyzed preoperatively, 1 year after surgery and at the final follow-up. SF-36 component scores (physical component summary (PCS) and mental component summary (MCS)) were used to evaluate the QoL. Results: Shoulder forward flexion and abduction measured in degrees improved from 86 (SD 14.5) and 82 (SD 33.8) preoperatively to 140 (SD 27.3) and 138 (31.3) at 1 year postoperatively. After a median follow-up of 17 years, mean shoulder functions were slightly lower than at 1 year postoperatively, but still better than preoperative function, ie, forward flexion 121 (SD 41.9) and abduction 122 (SD 44.5). The mean PCS score at the final follow-up was 41.9 (SD 9.7), and the mean MCS score was 49.9 (SD 12.5). Better shoulder function at the final follow-up was significantly associated with higher QoL in terms of PCS scores (P = .023), but not MCS scores (P = .287). Conclusion: The results of the present study indicate that PM transfer augmented with an achilles tendon allograft for scapular winging due to LTN palsy leads to functional improvements that persist in long term. These functional improvements likely translate to better QoL based on their association.