Background: Prospective evidence of associations of dietary patterns with cognitive decline is limited and inconsistent. We examined how cognitive changes among Chinese older adults relate to either an adapted Mediterranean diet score or factor analysis-derived dietary patterns. Methods: This prospective cohort study comprised 1,650 adults ≥55 years of age, who completed a cognitive screening test at two or more waves of the China Health and Nutrition Survey in 1997, 2000, or 2004. Outcomes were repeated measures of global cognitive scores, composite cognitive z scores (standardized units [SU]), and standardized verbal memory scores (SU). Baseline diet was measured by 24-hour recalls over 3 days. We used linear mixed effects models to evaluate how changes in cognitive scores were associated with adapted Mediterranean diet score and two dietary pattern scores derived from factor analysis. Results: Among adults ≥65 years of age, compared with participants in the lowest tertile of adapted Mediterranean diet, those in the highest tertile had a slower rate of cognitive decline (difference in mean SU change/year β = 0.042; 95% confidence interval [CI]: 0.002, 0.081). A wheat-based diverse diet derived by factor analysis shared features of the adapted Mediterranean diet, with the top tertile associated with slower annual decline in global cognitive function (β = 0.069 SU/year; 95% CI: 0.023, 0.114). We observed no associations among adults <65 years of age. Conclusions: Our findings suggest that an adapted Mediterranean diet or a wheat-based, diverse diet with similar components may reduce the rate of cognitive decline in later life in the Chinese population.