This article argues that it is possible to explain the European Union's reluctant attitude towards Turkey's membership in the EU on the basis of the EU's international and security identity and Turkey's security culture and perception of Europe. The EU's final decision on Turkey's accession is dependent both on Turkey's performance in adopting the EU's distinctive security identity and on the continuation of the EU member-states' commitment to turning the EU into an international actor with vital security interests in Turkey's vicinity. On the basis of this reasoning, the article reaches two main conclusions. The first is that the prospects for Turkey's EU membership are better in the post-11 September era than they were in the 1990s. The second is that there is a close relationship between the way the EU accession process unfolds and the way Turkey and the EU see each other. The longer the accession process lasts and the more ambiguously the EU reacts towards Turkey's membership, the more likely Turkey and the EU will view each other as 'security threats' rather than 'security providers'.