OBJECTIVE A substantial number of elderly people suffer from cognitive impairment and dementia, which are considered to have various risk factors, including masticatory dysfunction; however, the association between mastication and cognition is inconclusive. The objectives of this systematic review were to provide an overview of the literature on (1) the association between mastication and cognitive function and (2) the association between mastication and dementia incidence, in elderly people. METHODS Searches were conducted on five electronic databases (PubMed, EMBASE, CINHL, Cochrane Library, and Pro Quest) and publications were selected that met the following criteria: published between 2005 and 2015, written in English, and assessed associations between mastication and cognitive function, cognitive decline and dementia among population over 40 years old. The included publications were analyzed for study design, main conclusions, and strength of evidence by two reviewers who screened all abstracts and full-text articles, abstracted data and performed quality assessments by using a critical appraisal tool. RESULTS A total of 33 articles (22 cross-sectional, and 11 prospective cohort studies) were evaluated. Poorer mastication was associated with lower cognitive function in 15 of the 17 cross-sectional studies and steeper decline in 5 of the 6 prospective studies. Poorer mastication was one of significant risk factors for having dementia or mild memory impairment (MMI) in 4 of 5 cross-sectional studies and for the incidence of dementia or MMI in 4 of 5 prospective studies. CONCLUSIONS Most studies point to a positive association between mastication and cognitive function, including dementia among elderly people.