OBJECTIVES: The primary aims of this review were to identify studies investigating the association between the MedDiet pattern and age-related cognitive function, to determine the current status of knowledge, and to ascertain whether a lack of standardization with the operationalization of age-related cognitive function and differences in the chosen neuropsychological assessment methodology impacted on the results and findings. METHODS: The systematic review protocol for this paper was carried out following the statement and general principles of PRISMA and the UK Centre for Reviews and Dissemination (CRD). RESULTS: A systematic search of electronic databases yielded two cross-sectional studies, two cross-sectional/prospective studies, and 11 prospective studies for inclusion. Among this group of studies, conflicting results and conclusions regarding the efficacy of the MedDiet as a therapeutic approach for age-related cognitive function were found. Of importance, clear differences among studies in relation to neuropsychological assessment methodology were identified. Such disparity appeared to be one plausible factor contributing to the lack of consensus among study findings. DISCUSSION: One of the important challenges for future research will be to aim toward some kind of standardized neuropsychological assessment criteria. This type of endeavor will enable the ability to validate with greater confidence, whether or not adherence to a MedDiet does promote benefit for age-related cognitive function.