Can the HEXACO personality dimensions and facets be used to explain the principal-agent problem and the disposition effect? The proposed research is designed to address the relationship between personality dimensions and individuals’ propensity to engage in self-interested behavior (agency effect) and irrational investment decisions (disposition effect). This paper proposes a correlational study that will be one of the first to apply Ashton and Lee’s (2009) HEXACO framework of personality to examine the association between the six personality dimensions and measurements of the agency and disposition effect. The HEXACO model of personality dimension includes Honesty-Humility, Emotionality, Openness to Experience, Extraversion, Conscientiousness, and Agreeableness. Total participants in both experiments will be 480 undergraduate college students. Participating students will complete the HEXACO-60 self-report inventory and take part in a stock simulation where measurements of interests are recorded. Higher scores along the Honesty-Humility and Emotionality dimensions are expected to have a strong negative relationship with the agency effect measurement, while Openness to Experience, Conscientiousness, Agreeableness, and Extraversion will have a weak to moderate positive association. Higher scores along the Emotionality dimensions are expected to have a strong negative association with the disposition effect measurement, while lower scores of Conscientiousness are expected to have a positive relationship.