In the last decades, International Organizations (IOs) not only had their number and diversity multiplied, but also expanded significantly their attributions, their interests and their playing field. Furthermore, IOs started to deal not only with the international system and its governance. They also began to act in order to influence, with several objectives and in a variety of ways, the domestic behavior of their member states, i.e., their public policies. The article searches, mainly through a synthesis of the scant academic literature that deals with IOs as policy diffusers, to analyze the objectives and forms of action of IOs in such processes, as well as the multiple instruments they employ to guide the domestic performance of the sta...