Research on international norms has yet to answer satisfactorily some of our own most important questions about the origins of norms and the conditions under which some norms win out over others. The authors argue that international relations (IR) theorists should engage more with research in moral psychology and neuroscience to advance theories of norm emergence and resonance. This Element first provides an overview of six areas of research in neuroscience and moral psychology that hold particular promise for norms theorists and international relations theory more generally. It next surveys existing literature in IR to see how literature from moral psychology is already being put to use, and then recommends a research agenda for norms researchers engaging with this literature. The authors do not believe that this exchange should be a one-way street, however, and they discuss various ways in which the IR literature on norms may be of interest and of use to moral psychologists, and of use to advocacy communities.