This study intends to point out that integrating the whole Balkan Peninsula within the European project is essential from security aspect. Deepening or enlarging the European Union has been a debate for decades. Unifying the continent, however, not only a project but a need as well. The Balkan Peninsula is the last region to wait for membership after the mass enlargement in 2004. Moreover, recent events in international relations showed cases when security was directly violated. Train camps of extreme groups, criminals mingled among asylum seekers, last but not least the activities of the human traffickers in the Mediterranean should not be treated on the level of irregular migration or border security only. This phenomenon should be investigated from two aspects: one from EU security issue and the security interest of the non-EU members in the Balkan Peninsula. The study seeks to point out that the two interests should be harmonised, and before the accession negotiations are completed, a common strategy should be worked out on behalf of the EU and its Member State on one side, and the candidate countries, on the other side.