Dementia is a major global health challenge, as its burden on society will increase with population aging. Given the lack of effective pharmaceutical treatment for common types of dementia including Alzheimer's disease and vascular dementia, research interest in lifestyle modifications that could prevent, postpone the clinical syndrome or decelerate progression of dementia is growing. Among the various dietary patterns that were tested for their effects on cognition, the traditional Mediterranean diet (MeDi) has shown promising results. This review aims to summarize the epidemiological evidence on the effects of MeDi on the prevention of dementia, presenting data from cross-sectional as well as longitudinal observational studies conducted both in Mediterranean and non-Mediterranean countries. These findings have been also reproduced in the context of one recent randomized-controlled clinical trial. Postulated mechanisms of action that may account for the potential protective effect of MeDi on cognitive impairment will be briefly discussed. Despite the fact that the link between MeDi and cognitive decline has been only explored for less than a decade, data on efficacy is rapidly increasing and allows optimism that MeDi could emerge as an alternative prophylactic treatment for dementia.