(1) Background: The purpose of this study was to determine whether the drooling of adult patients with diverse central nervous system diseases can be treated with botulinum toxin type A. (2) Methods: The Cochrane Library, MEDLINE, and Embase were all searched for studies that fit the inclusion criteria. The patients in the studies had to be adults (>18 years old), and the studies had to be randomized placebo-controlled trials, controlled trials, or prospective studies. Each study had to have enough quantifiable data available for meta-analysis. The primary outcome measure was the Drooling Severity and Frequency Scale (DSFS). (3) Results: The meta-analysis comprised three studies. A statistically significant difference in DSFS score between the treatment and control groups was observed in the meta-analysis, with an overall standardized mean difference of −0.9377 (95% CI, −1.2919 to −0.5836;p< 0.0001). A total of seven studies were ineligible for inclusion in the meta-analysis and were only assessed as qualitative data. All qualitative studies showed a significant reduction in DSFS score a few weeks or months after the injection of botulinum toxin. (4) Conclusions: Botulinum toxin type A is safe and effective as a treatment for drooling in adult patients with central nervous system diseases.