The aim of this chapter is to provide some reflections that may aid in the establishment of a theoretical framework for the assessment of competition, cooperation, and solidarity in EU law. After providing a working definition of these notions, the chapter explores how they are conceived in the context of different federal models, including the EU. It argues that the real issue in trying to establish the role of competition, cooperation, and solidarity in any given federal model does not depend on an inevitably simplistic characterization as ‘cooperative’ or ‘competitive’, but instead on the specific constitutional configuration of the polity and the relative strength and weakness of its substantive competences. An assessment of those factors in the EU context shows that the EU legal order not only creates conflicts between solidarity and competition (especially in the context of the internal market and economic governance), but also often decides them in favour of the latter. Considering that integration primarily through competition, rather than solidarity, may not be a stable and sustainable course of action in the long run, the chapter finally develops some tentative proposals to foster a degree of reciprocity-based solidarity in the EU legal and political order.