It’s widely accepted that whether or not an agent merits praise for performing a particular action importantly depends on her motivation in doing so. What has received less attention is the importance of an agent’s moral understanding to whether she merits praise for performing a particular action, or whether her action has ‘moral worth.’ The first task of this paper is relatively straightforward: to show that two prominent attempts to address the importance of moral understanding to moral worth, namely that (...) of Zoe Johnson King and Paulina Sliwa, are unsuccessful. The second task of this paper, which is more novel and ambitious, is to show that agents who lack moral understanding are a challenge to more accounts of moral worth than has been previously recognized. My goal in this paper is largely negative: to show that extant accounts of such conditions are unable to account for the relevance of an agent’s understanding to her praiseworthiness for performing a particular action. In making clear these shortcomings, however, I also hope to make clear just how complicated it is to pin down exactly when an agent merits praise for her actions. (shrink)