People differ in how much personal importance, and moral relevance, they ascribe to epistemic rationality. These stable individual differences can be assessed using the Importance of Rationality Scale (IRS), and Moralized Rationality Scale (MRS). Furthermore, these individual differences are conceptually distinct, and associated with different cognitive, affective, and behavioral outcomes. However, little is known about what signifies and differentiates people who score high (vs. low) on the IRS and MRS respectively, and where these individual differences stem from. In the present research we begin to address these questions by examining how these epistemic values relate to the Big Five personality traits. Two studies consistently show that both the IRS and MRS are positively related to Openness to experience. However, only the MRS is negatively associated with Agreeableness, and only the IRS is positively associated with Conscientiousness.