ABSTRACT: In this paper, I discuss a new problem for moral realism, the problem of moral aliens. In the first section, I introduce this problem. Moral aliens are people who radically disagree with us concerning moral matters. Moral aliens are neither obviously incoherent nor do they seem to lack rational support from their own perspective. On the one hand, moral realists claim that we should stick to our guns when we encounter moral aliens. On the other hand, moral realists, in contrast to anti-realists, seem to be committed to an epistemic symmetry between us and our moral aliens that forces us into rational suspension of our moral beliefs. Unless one disputes the very possibility of moral aliens, this poses a severe challenge to the moral realist. In the second section, I will address this problem. It will turn out that, on closer scrutiny, we cannot make any sense of the idea that moral aliens should be taken as our epistemic peers. Consequently, there is no way to argue that encountering moral aliens gives us any reason to revise our moral beliefs. If my argument is correct, the possibility of encountering moral aliens poses no real threat to moral realism.