As a normative ethical theory, ethical egoism may seem compatible with the metaethical theory of moral realism. However, in this article, I will problematize such an assumption. The reason is that an important motivation for rejecting moral anti-realism by many moral realists—like Derek Parfit, Torbjörn Tännsjö, and Erik J. Wielenberg—is that such a view entails that not even cruel or horrendous acts are to be called wrong by any universal or objective standard. I suggest that this motivation also applies to the ethical theory of egoism, as it may imply that no one has any obligation to refrain from cruel or horrendous acts as long they are beneficial to the agent. On that basis, I will demonstrate that egoism is a problem for robust moral realists that also, to a large degree, is being overlooked.