The effect of botulinum toxin A (BoNTA) on non-motor symptoms (NMS) in patients with cervical dystonia remains an area of significant clinical interest, given the profound impact of these symptoms on patients' quality of life. While the therapeutic efficacy of BoNTA in alleviating motor symptoms of cervical dystonia is well established, its impact on NMS such as depression, anxiety disorder, and sleep disturbance requires further investigation. This systematic review synthesizes the latest evidence on the effects of BoNTA on these selected non-motor symptoms. A comprehensive search of the PubMed, Web of Science, and Scopus databases identified 266 articles, of which eight studies met our strict inclusion criteria. Pre- and post-intervention changes in depression, anxiety, and sleep disturbance were assessed in a total of 280 adult patients with cervical dystonia treated with BoNTA. The results indicate that BoNTA has a positive effect on depressive symptoms, with most studies showing a statistically significant improvement after treatment. Similarly, studies are reporting significant reductions in anxiety scores following BoNTA treatment. However, the effects of this treatment method on sleep disturbances were less conclusive, with none of the reviewed studies showing significant improvements in sleep quality or daytime sleepiness. The results highlight the potential of BoNTA to positively influence non-motor symptoms, particularly depression and anxiety, in patients with cervical dystonia, although its effects on sleep remain unclear. These findings underscore the need for further research to fully understand the mechanisms underlying the non-motor effects of BoNTA and to develop comprehensive treatment strategies.