As an increasingly popular interdisciplinary and multi-method approach to studying individual-level political phenomena, political psychology has made important strides in explaining the processes behind political attitudes and behaviour, decision making, and the interaction between the individual and the group. Hence, it is in a unique position to improve the explanatory power of international relations research that deals with the individual, such as in the study of leadership, foreign policy decision making, foreign policy analysis, and public opinion. After discussing the defining characteristics of political psychology, the research trends in the field, and its research methods, the article reviews the existing and potential contributions of political psychologyto the study of international relations. Next, the article points to new areas for research in international relations that would particularly benefit from the theories and the methods already in use in political psychology.