How can we account for the global diffusion of remarkably similar policy innovations across widely differing nation-states? In an era characterized by heightened globalization and increasingly radical state restructuring, this question has become especially acute. Scholars of international relations offer a number of theoretical explanations for the cross-national convergence of ideas, institutions, and interests. We examine the proliferation of state bureaucracies for gender mainstreaming. These organizations seek to integrate a gender-equality perspective across all areas of government policy. Although they so far have received scant attention outside of feminist policy circles, these mainstreaming bureaucracies—now in place in over 100 countries—represent a powerful challenge to business-as-usual politics and policymaking. As a policy innovation, the speed with which these institutional mechanisms have been adopted by the majority of national governments is unprecedented. We argue that transnational networks composed largely of nonstate actors (notably women's international nongovernmental organizations and the United Nations) have been the primary forces driving the diffusion of gender mainstreaming. In an event history analysis of 157 nation-states from 1975 to 1998, we assess how various national and transnational factors have affected the timing and the type of the institutional changes these states have made. Our findings support the claim that the diffusion of gender-mainstreaming mechanisms has been facilitated by the role played by transnational networks, in particular by the transnational feminist movement. Further, they suggest a major shift in the nature and the locus of global politics and national policymaking.