An short Food Frequency Questionnaire (FFQ) was developed for online assessment of adherence to the Dutch Mediterranean-DASH Diet Intervention for Neurodegenerative Delay (MIND-NL) diet, a culturally adapted version of the original American MIND diet. This study aimed to evaluate the relative validity of this short FFQ for assessing adherence to the MIND-NL diet, as scored by the MIND-NL score, compared to three-day food records among community-dwelling older adults at risk of cognitive decline (N=1078; 67.4±4.6 years; 64% female). A combination of statistical methods was used to assess the relative validity: presence of bias by Bland-Altman analysis; strength of association with Kendall’s Tau-b and Spearman correlation coefficients; and levels of agreement with Wilcoxon signed rank test, cross-classification, and weighted Kappa (κ) statistics. The Kendall’s Tau-b correlation for the MIND-NL score was 0.33 (95% CI: 0.29-0.37; de-attenuated Tau-b: 0.45). Individual MIND-NL diet component score correlations ranged from 0.05 to 0.56, with 12 out of 15 of the MIND-NL diet components adequately correlated (>0.20). The average MIND-NL scores for the short FFQ (8.4±1.8 points) and food records (6.7±1.7 points) showed to be significantly different (P<0.001). The Kappa (κ) coefficient for tertile classification of the MIND-NL score was 0.29 (95% CI: 0.25-0.33), indicating an acceptable level of agreement in ranking participants beyond chance. Acceptable agreements (κ >0.20) were observed for 10 out of 15 MIND-NL diet components. Taking all analyses together, the short FFQ showed acceptable validity for ranking older adults at risk of cognitive decline according to their adherence to the MIND-NL diet.