Scholarship has long suggested that, in the decades of mass migration, Italian subversives were part of a global network based on the worldwide circulation of radical ideas and activists. Yet historiography has studied such dynamics mainly in the receiving countries and has tended to overlook the Italian side of those interactions. This article examines Italian migrants’ development of political and labor militancy in a transnational perspective. It focuses primarily on the contribution of the experience abroad to Italian radicalism and offers a few examples of the influence that migrants tried to exert, directly or indirectly, in their native country. On the one hand, expatriates often invested part of their remittances to support workers’ mutual aid societies, local unions, political newspapers, and strikes. On the other, returnees were able to draw on the new strategies and ideas they had learned abroad when taking part in the class struggle and political battles in Italy.