The European Union has been recognised as an international system whose decisions and actions are conditioned by environmental determinants, which is a dynamic process of change. The article attempts to explain the EU’s decisions based on the conclusions of the European Council in 2010–2022. 93 documents containing the conclusions of the European Council adopted during that period were analysed. It was found that the determinants of EU decisions and actions function – firstly – at the international system level and, secondly, at the level of the domestic systems of the Member States. In addition, the article: 1) reconstructed the discussion in the science of international relations on behavioural determinants, 2) reconstructed the perception of determinants in the conclusions of the European Council; 3) a model for organising the analysis of the determinants of the decisions of the European Council was proposed.

The European Union has been recognised as an international system whose decisions and actions are conditioned by environmental determinants, which is a dynamic process of change. The article attempts to explain the EU’s decisions based on the conclusions of the European Council in 2010–2022. 93 documents containing the conclusions of the European Council adopted during that period were analysed. It was found that the determinants of EU decisions and actions function – firstly – at the international system level and, secondly, at the level of the domestic systems of the Member States. In addition, the article: 1) reconstructed the discussion in the science of international relations on behavioural determinants, 2) reconstructed the perception of determinants in the conclusions of the European Council; 3) a model for organising the analysis of the determinants of the decisions of the European Council was proposed.