North Atlantic Treaty Organization (NATO) was formed by the United States, Canada and some Western European countries in 1949 as a well-equipped and structured military organization with having the purpose to provide security to its member states from any external threats in general and the Soviet Union and its allies in particular. During the Cold War, signing of Warsaw Pact treaty by the Soviet Union and its allies, and their attempt to achieve parity of power with the Western bloc, propelled NATO to accomplish its objective by deterrence alone. After collapse of the Soviet Union, NATO was expected to end its relevance in the post-Cold War era but, through expanding its role and functions to other areas such as crisis management and peace keeping operations, promoting and strengthening democracy, enlargement of its member states, ‘out of area' operations and fight against global challenges etc, it has transformed itself from collective defense to collective security organization. The study addresses on why and how it has involved in ‘out of area' operations? To provide empirical input to the study, Afghanistan has taken as a case study. The study further highlights how NATO faced difficulties in civilian resources for this operation and for that reason it seeks cooperation from other International Organizations like EU and UN. It further discusses on various attainments and challenges in reconstructing socio-economic-political and military systems of Afghanistan. It throws light on its impacts over the region and the possibility of conflicts among member states and international organization in future.