Background and Objective: The Mediterranean-dietary approach to stop hypertension (DASH) Intervention for Neurodegenerative Delay (MIND) is n healthy dietary plan which showed protective effects on cognitive decline, cognitive performance, and dementia risk. Selenium is an element with nutritional and toxicological properties, whose role in neurological diseases is greatly debated. We aimed to perform individual-level selenium speciation analyses to understand the association of different selenium compounds (organic and inorganic) with MIND diet adherence. Methods: We recruited healthy and non-smoking blood donors from Northern Italy referred to the Transfusion Medicine Unit of Reggio Emilia Hospital in 2017-2019 period. We assessed adherence to MIND diet using the semi-quantitative EPIC-food frequency questionnaire, and total selenium and its species in serum. We used cubic spline regression analysis to investigate the association between selenium compounds and adherence to the MIND diet. Results: Out of 148 subjects, we performed serum speciation analyses 104 (males/females: 50/54), with median age 48.5 years. Median score of adherence to the MIND diet was 7.5 (interquartile range (IQR) 6.5-8.5), while median levels of total selenium were 116.5 µg/L (IQR 106.0-128.0 µg/L). Overall, we found that total selenium was negatively and linearly correlated with adherence to MIND diet, as in the case of organic selenium and the organic form selenoprotein P. Glutathione peroxidase-bound selenium and selenocysteine were U-shaped associated with MIND, with positive associations above 8-score. For inorganic selenium and specifically the selenate compound, an inverted U-shaped relation emerged with MIND diet, with negative relation above median level of adherence. Conclusions: Our results support the hypothesis that higher adherence to MIND corresponds to lower levels of selenium in serum, specifically selenoprotein P and selenate. Hence, these two compounds may have adverse effects on cognitive decline and dementia risk as suggested in recent studies.