This volume examines the state of social Europe when European Union principles and policies have to be implemented in the member states while the EU legitimacy crisis and the Great Recession prevail. The volume explores diverse processes, stages and subjects of implementation in a variety of social policies to identify different institutional dynamics and actor behaviours at play. The individual contributions examine the transposition of the patients’ rights directive to the Europeanisation of pension reforms; the role of national parliaments in transposing social Europe; judicial Europeanisation; and the multi-level enforcement of EU decisions. Theoretically, the volume highlights that implementation is often conditioned by domestic politics or comes as a ‘random walk’ due to organisational and cognitive constraints. Empirically, the volume has three main findings. First, the constitutive components of the EU tend to have a contradictory impact on the EU’s social policies and the national welfare systems. Second, crises influence the implementation of social Europe, at times leading to a modification of fundamental principles and content, but not across the board. Third, as a result, there is evidence of differentiated Europeanisation.