This study seeks to explore the reasons why joint membership in NATO could not help Turkey and Greece resolve their long-standing territorial disputes in a problem solving win-win framework, based on the transformation of their realpolitik security cultures into non-realpolitik security cultures. In undertaking this task, this article employs a partly theoretical and partly empirical perspective. The theoretical part assesses the expectations of various international relations theoretical accounts of the impact of international institutions/organizations on behaviors of states. There exist two main theoretical currents that aim at analyzing such a relationship. While rationalistic-institutionalist approaches confine the impact of international institutions/organizations only to behaviors of states, sociological-institutionalist approaches argue that institutional linkages not only shape and constrain states' behavioral strategies but also reconstruct their identities and interests. The empirical part of t...