This article seeks to explore the way in which the Court of Justice of the European Union (‘CJEU’) has interpreted and applied the principle of democracy. It examines first the democratization process upon which the EU has embarked since the adoption of the Treaty of Maastricht and how that transformation was a positive reaction to those voices arguing that the EU suffers from a ‘democratic deficit’. Next, it is argued that the CJEU has understood the principle of democracy in a way which is respectful of the two sources of democratic legitimacy at EU level, namely the Member States and the peoples of Europe. Accordingly, that understanding of the principle of democracy is illustrated by some relevant examples taken from the case law of the CJEU and the European General Court (‘EGC’). Those examples show that the CJEU has strived to protect the prerogatives of the European Parliament, the only political institution of the EU whose members have, since 1979, been elected for a term of five years by direct universal suffrage in a free and secret ballot. Yet, they also show that the principle of democracy is not limited to protecting parliamentary prerogatives. That principle, like all EU constitutional principles, pervades the whole of EU law and, as such, must be read in light of societal changes. As democracy within the EU is not limited to the participation by the European Parliament in the legislative process but also encompasses other forms of governance, in particular rule-making by administrative agencies and the achievement of consensus by social partners, it is for the EU judiciary to make sure that those other forms of governance remain as democratic as possible. This can be achieved, inter alia, by making sure that they enjoy sufficient representation or are subject to parliamentary control. Furthermore, the CJEU and the EGC also take into account new mechanisms which seek to strengthen the principle of democracy, such as the principle of transparency. In so doing, they aim to enhance the democratic legitimacy of the EU by providing sufficient means for EU citizens to hold their representatives accountable. Finally, it is contended that the principle of democracy, as interpreted by the CJEU, draws inspiration from national democracies. In so doing, the CJEU strives to place national and supranational democracies in a mutually reinforcing relationship.