The most internationalist of all party families, the radical left has paradoxically always lagged behind in its cooperation at the EU level. The previous decade, however, the transnational character of the Eurozone crisis and its austerity-centred management provided a strong incentive to remedy that. By focusing on the relations between three prominent members of this party family at the time (SYRIZA, Podemos, Left Bloc), this book shows how and why the transnational cooperation on the radical left largely failed to deliver in a propitious context. With implications for the study of other party families, the book lays out the key factors that prevented the European radical left from coming together to provide an alternative to the neoliberal status quo in the EU.