Results from numerous studies suggest protective effects of the Mediterranean diet for cardiovascular disease, cancer, and mortality. Evidence for an association with a decreased risk of cognitive decline is less consistent and studies are limited by a lack of diversity in their populations.We followed 2,326 older adults (38.2% black, 51.3% female, aged 70-79 at baseline) over 8 years in a prospective cohort study in the United States (Health, Aging and Body Composition study). To measure adherence to a Mediterranean diet, we calculated race-specific tertiles of the MedDiet score (range: 0-55) using baseline food frequency questionnaires. Cognitive decline was assessed using repeated Modified Mini Mental State Examination scores over the study. We used linear mixed models to assess the association between MedDiet score and trajectory of cognitive decline.Among blacks, participants with high MedDiet scores had a significantly lower mean rate of decline on the Modified Mini Mental State Examination score compared with participants with lower MedDiet scores (middle and bottom tertiles). The mean difference in points per year was 0.22 (95% confidence interval: 0.05-0.39; p = .01) after adjustment for age, sex, education, body mass index, current smoking, physical activity, depression, diabetes, total energy intake, and socioeconomic status. No association between MedDiet scores and change in Modified Mini Mental State Examination score was seen among white participants (p = .14).Stronger adherence to the Mediterranean diet may reduce the rate of cognitive decline among black, but not white older adults. Further studies in diverse populations are needed to confirm this association and pinpoint mechanisms that may explain these results.