The objective of the research is to define the development of constitutionalism and socio-cultural challenges related to the formation process of the European Union’s legal identity. To achieve this goal, the concept of constitutionalism and its changes during the period of the European Union’s development are examined. Tendencies of the European Union Member States’ constitutionalism process are analysed and socio-cultural tensions of the formation of the contemporary European Union’s legal identity, which arise between security and freedom, order and justice and government and society are identified. The article states that the sustainability of public democratic processes and the functioning of the European Union is possible only if the constitutional values are protected. The reseach also reveals that the further evolution of European constitutionalism and legal identity still needs to enhance the development of the rules which could influence the creation and activities of the independent, self-governing EU’s political community.