The main aim of this study is to find out whether or not, and to what extent the European Neighbourhood Policy contributes to European security in the light of effects of changing international structure on European scale. To that end, a neo-realist approach is applied in the study, and it is argued that in which ways the changing political structure affects foreign and security policies and security perceptions of European great powers since the end of the Cold War, and in which ways the European Neighbourhood Policy, especially its sub-policy the Eastern Partnership, has influence on these perceptions. The first chapter of the thesis defines basic neo-realist assumptions and two other important concepts, namely security and neighbourhood, in order to draw a framework for evaluate European security. Following part of the first chapter analyses the current political structure in multipolar Europe and policies of European great powers to examine the environment in which the European Neighbourhood Policy/the Eastern Partnership is pursued. The second chapter defines main motivations, aims and tools of the Policy from neo-realist perspective, and its geopolitical components. In light of assumptions of these chapters, the last chapter argues role of the European Neighbourhood Policy to provide European security by evaluating the recent Ukrainian crisis, taking Russia's policies and perceptions on the Policy into account. To conclude, this study claims that the European Neighbourhood Policy in multipolar structure of contemporary Europe is counter-productive for European security, creating geopolitical competition and new threats based on the traditional understandings of security.