Although the rule of law is a normative notion, it requires a multidimensional approach. It speaks to important issues of law and politics, and its respect is essential for both legal and social security. It can be observed within the European Union (EU) where the issue of respect for the rule of law by its Member States has gained particular importance. The main goal of our study is to contribute to the academic discourse concerning the EU rule of law. The analysis particularly considers the approaches adopted by the EU institutions to the definition of this concept. Consequently, the first part of the article concentrates on difficulties in defining the rule of law. The second part presents the evolution of the Court of Justice approach toward this concept. The next part contains the analysis of the attitudes presented by other EU institutions in their documents. In the conclusions, it is underlined that although the approaches of the EU institutions towards the rule of have evolved, and they have tried to define it and indicate its main components, certain issues require clarification, e.g., the relations of the rule of law with other values.