This thesis provides an account of the nature of intellectual vice. An intellectual vice is an aspect of someone’s character that makes them a bad intellectual agent, or bad knower. Previous accounts of the intellectual vices have tended to identify them with either the disposition to have bad epistemic motivations, or the disposition to produce bad epistemic effects. I argue for a new view that can overcome the difficulties faced by both of these accounts. According to this view, there are two distinct forms of intellectual vice: vices that involve motivations towards bad epistemic ends, and vices that involve some entrenched pattern of bad judgement.