Judicial institutions have become the standard solution to umpire multilevel polities across much of the European continent. However, such arrangement is not free from complexities. This paper analyses the problems associated with the construction of legitimacy regarding constitutional courts in European multilevel democracies. In these polities, constitutional courts tend to rely on three different forms of legitimacy, which are embedded into their institutional design: democratic, multilevel; and technocratic. However, these forms of legitimacy are in tension, often undermining one another when combined. Furthermore, this tension is exploited by political actors to attack the courts, resulting in reputational costs for these institutions.