This thesis aims to understand changing energy security considerations of the European Union and in this context Turkey’s increasing chance to be a European member. In order to do that, the study targets the question : “How did European energy security considerations enhance and how does this situation influence Turkey’s possible membership process, due to latter’s geo-strategic position?”. European Union, as the other import-energy dependent actors, has experienced the negative consequences of this dependency. Particulary, the energy’s being used as a political weapon has made the “energy security” more momentous for the Community. In this respect, energy security policies has attracted more attention. As a result of one of these policies, diversification, the Union has started to give more consideration to diversified energy suppliers and transit countries. Accordingly, Turkey has gained a significant attention as an iv important transit country, with the strategic position near to main energy suppliers. Thus, this thesis proposes that Turkey’s geo-strategic position will enhance Turkey’s significance for the Union and open the way for its Union membership. Relying on official EU documents and literature, this study reaches the conclusion that energy security is very important for the EU and in order to enhance its situation the Union will try its best. In this regard, Turkey’s religious and cultural diffrences seems to be less important than Union’s interests and thus Turkey has an enhanced possibility to be an EU member.