This book defends the view that epistemic vices are blameworthy or otherwise reprehensible character traits, attitudes, or ways of thinking that systematically obstruct the gaining, keeping, or sharing of knowledge. An account is given of specific epistemic vices and of the particular ways in which they get in the way of knowledge. Closed-mindedness is an example of a character vice, an epistemic vice that is a character trait. Epistemic insouciance and epistemic malevolence are examples of attitude vices. An example of an epistemic vice that is a way of thinking is wishful thinking. Only epistemic vices that we have the ability to control or modify are strictly blameworthy but all epistemic vices are intellectual failings that reflect badly on the person whose vices they are. Epistemic vices merit criticism if not blame. Many epistemic vices are stealthy, in the sense that they block their own detection by active critical reflection or other means. In these cases, traumatic experiences can sometimes open one’s eyes to one’s own failings but are not guaranteed to do so. Although significant obstacles stand in the way of self-improvement in respect of our epistemic vices, and some epistemic vices are resistant to self-improvement strategies, self-improvement is nevertheless possible in some cases.