Several studies suggest an association between hypovitaminosis D and basic and executive cognitive functions, depression, bipolar disorder, and schizophrenia. A recent study confirms neophobic responses in vitamin D receptor mutant mice. We explored whether the plasma levels of 1,25-dihydroxyvitamin D (1,25(OH)(2)D-3), the active form of vitamin D, are correlated with basic personality traits. A total of 206 healthy unrelated volunteers (108 male, 98 female, age 31 +/- 13 years) completed the German version of the NEO Five-Factor Inventory (NEO-FFI), which allows reliable and valid assessment of personality along the dimensions neuroticism, extraversion, openness to new experiences, agreeableness and conscientiousness. We found a significant correlation between 1,25(OH)(2)D-3 concentration and the factor extraversion (n = 206, r = 0.202, p = 0.004) and the factor openness (n = 206, r = 0.148, p = 0.034). The possible mechanisms by which 1,25(OH)(2)D-3 acts on the brain might include Ca2+ signaling, buffering antioxidant, and anti-inflammatory defenses against vascular injury, stimulating neurotrophins and improving metabolic and cardiovascular function. In conclusion, we suggest that 1,25(OH)(2)D-3 might influence personality traits, promoting extrovert and open behavior.