In recent years, multiple crises (the global financial crisis, the refugee crisis and security crisis) have tested to the limits the European integration project. Relying on the principle of solidarity, which is enshrined in the Treaty articles, the EU has sought to ease the strain of the most exposed countries with the adoption of measures of burden-sharing. This has led to divergent reactions among member states and to a still open debate over the meaning, and implications, of concrete EU solidarity. Drawing on different strands of literature and using EUENGAGE survey data on ten EU countries, this chapter explores citizens’ and politicians’ support for EU burden-sharing measures across the three areas that have been most severely hit by the crises, namely, financial, migration and security policies. In so doing, we first seek to account for the variation in the level of support for burden-sharing arrangements both across policy areas and member states. Then, we explore whether and to what extent such support is driven by cost–benefit motivations or, rather, by a genuine sense of EU solidarity. Finally, with a particular focus on the tension between national sovereignty party claims and the logics of measures centred on a solidarity-based rationale that transcends national borders, we provide insights about the likely challenges to the development of feelings of solidarity across the EU. In so doing, this chapter shows that, though a possible socio-tropic effect of the exposure to the major crises can affect support for burden-sharing, the picture is actually more compounded and not just connected to a rational cost–benefit logic.