ABSTRACT Objective: This study comprises a systematic review and meta-analysis that aimed to estimate the prevalence of dementia in long-term care institutions (LTCIs). Methods: We used the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA). Original transversal and longitudinal articles published until July 2020 were eligible in this review. Databases PubMed/MedLine, Web of Science, Scopus and ScienceDirect were searched. Overall prevalence and confidence intervals were estimated. Heterogeneity was calculated according to the index of heterogeneity (I2). Results: One hundred seventy-five studies were found in all databases and 19 studies were meta-analyses, resulting in an overall prevalence of 53% (CI 46-59%; p < 0.01) of demented older adults living in LTCIs. Conclusion: Prevalence of dementia is higher in older adults living in LTCIs than those living in general communities. This data shows a worrying reality that needs to be changed. There is a need for a better understanding of the elements that cause this increase in dementia in LTCFs to direct actions to improve the quality of life and health of institutionalized elderly.