- The HEXACO personality framework is an emerging perspective to explain the phenotypic structure of personality, and is believed to replicate across natural language lexical studies better than the Five-Factor Model. Although similar to the “Big Five,” the primary difference between the two structural models is the recovery of the Honesty-Humility dimension, a dimension related to sincerity, fairness, and modesty. This trait has also been associated with behavioral under-control and increased risk-taking, but its association with rational responding has yet to be explicated. In the current study, we test the associations between HEXACO personality dimensions and decision-making competence (DMC), a variable that reflects individual differences in rational responding across several classic behavioral decision-making tasks (e.g., framing effects and following decision rules; Parker & Fischhoff, 2005). DMC has been shown to predict health behaviors and risk attitudes; however, little research has been conducted to examine the association between DMC and broad dispositional traits. Based on past research, we predicted that Honesty-Humility, Conscientiousness, and Openness, would be significantly associated with greater DMC. We recruited an online Italian community sample (n=804). Participants completed the HEXACO-PI-R questionnaire (Ashton & Lee, 2009) and subscales of the Italian-language DMC (del Missier et al., 2012). As expected, we found significant correlations for Honesty/Humility, r = .21, p < .01, Conscientiousness r = .28, p < .01, and Openness r = .17, p < .01. Extraversion, Agreeableness, and Emotionality (i.e., Neuroticism), was not related to DMC performance. Multiple regression analysis revealed that the six HEXACO dimensions accounted for 12% variance on DMC. Examining these associations at the facet-level, we found that for Honesty-Humility, that traits related to Honesty were associated with DMC scores, but not facets related to Humility. Holding each dimension constant, we found that Conscientiousness, Honesty/Humility and Openness uniquely accounted for variance in DMC scores. These results suggest that certain dispositional traits related to cognitive and behavioral control (e.g., Honesty/Humility and Conscientiousness) and open-minded thinking are associated with a greater tendency to engage in rational thought, which in turn, may be associated with better real-life decision quality.