Botulinum toxin (BTX) injections into the musculature surrounding the brachial plexus have been examined as a potential treatment for neurogenic thoracic outlet syndrome (nTOS). This systematic review identified 15 publications, of which one was a randomized controlled trial. BTX injections performed with ultrasound or electromyographic guidance, and with the inclusion of the pectoralis minor muscle, in addition to the anterior and/or middle scalenes, tended to provide greater symptom improvement and may predict response to first rib resection. Importantly, most studies were of low quality; thus, the results should be interpreted with caution. Further high-quality studies are needed to confirm these findings.