In this article, we outline the current state of research concerning cooperation in the cross-national context. We present several theoretical approaches and empirical findings regarding national differences in cooperation, as well as how cooperation may depend on the national background of the interaction partner. In addition, we discuss the influence of (national) group norms, cultural similarity, and ingroup membership. This review concludes with a call for research on cooperation to include more non-WEIRD nations and more systematically cover national background as one important social category determining the willingness to cooperate.