This article presents how two currently dominant theories of political integration – neo-functionalism and intergovernmental liberalism – address the issue of international security. To this end, the author describes the two theoretical concepts and their place in the broader context of the theory of international relations and presents the basic theoretical principles of these theories. The main research problem was analysed on two levels, with the principal purpose of answering the questions of how international security concerns are approached by theorists of neo-functionalism and intergovernmental liberalism and what elements of these theories can be seen in the practice of political integration of states. Since both concepts have been formulated in response to European integration, it is the European Union that is the most important reference point for the reflection on this practice.