Both poor oral health and cognitive decline are common problems among elders. The aim of this review article is to identify the role of oral health in the elderly cognitive decline. Available databases including Magiran, Google Scholar, SID, Medlib, Iranmedex, Proquest Elsevier, Ovid, Pubmed, and Science Direct was assayed by key words mouth and tooth, cognitive disorder, cognitive decline, cognitive impairment, dementia, oral health, aging, elder, ageing, older people, elderly. Relevant English and Persian articles from 2000 to the end of 2015 were used. Exclusion criteria included no access to full text and articles in other languages. 56 articles were extracted and finally 10 articles relevant to objectives of this study were examined. The results of all studies showed a significant relationship between the number of tooth loss and cognitive decline, however, only one study was designed longitudinally. Additional research seems necessary to prove relationship between oral health and cognitive decline.