This critical review accomplished two main tasks: first, the article provides scope for identifying the most common conceptions of moral competence in the scientific literature, as well as the different ways to measure this type of competence. Having moral judgment is the most popular element of moral competence, but the literature introduces many other elements. The review also shows there is a plethora of ways to measure moral competence, either in standardized tests providing scores or other non-standardized tests. As a (...) second task, the article reflects critically on the general use of the idea of moral competence. Results suggest that this idea functions as what philosopher Bernard Williams would have called a thin ethical concept. Thin concepts are not problematic in and of themselves if they are used as linguistic shorthand, however, there may be shortcomings in the literature on moral competence because the idea is not rooted in more substantive views or theories in a way that is both clear and coherent. (shrink)