INTRODUCTION: Multiple sclerosis (MS), as an autoimmune demyelinating disorder, is associated with cognitive dysfunction. Dementia can result from severe cognitive dysfunction or other pathways in MS, but the exact mechanisms and prevalence are unknown. OBJECTIVE: This review aimed to determine the pooled prevalence and risk of dementia in people with MS (PwMS). DESIGN: This meta-analysis was performed in accordance with the guidelines established by the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA). METHODS: Embase, PubMed, Web of Science, and Scopus were comprehensively searched up to August 29, 2024, to identify observational studies that examined the prevalence or hazard ratio (HR) of dementia among PwMS. This meta-analysis used a random-effects model to calculate the pooled prevalence and risk of dementia among PwMS, where the prevalence rate and HR were the main metrics for effect size. RESULTS: Ten studies, including a total of 37,831 PwMS, estimated the prevalence of dementia in PwMS to be 5.31% (I = 99.2%, 95% CI: 2.25%-11.98%). In addition, a meta-analysis of four studies assessed the HR of dementia among PwMS, revealing a pooled HR of 1.67 (p < 0.01, I = 73.5%, 95% CI: 1.31-2.13). CONCLUSION: While dementia is not a common feature of MS, PwMS still have a significantly higher risk of developing it, compared to healthy indiviuals. However, the considerable variability across studies indicates that these estimates should be interpreted with caution, as inconsistencies in research approaches may have influenced the results. These findings warrant further validation.