The collapse of the Socialist Federal Republic of Yugoslavia (SFRY) began in Slovenia and Croatia, and this disaster was discharged into Bosnia and Herzegovina and ended up in the last bastion of Kosovo. One of the longest and most critical wars in the former Yugoslavia was the inter-ethnic conflict between Kosovo Albanians and Serbs. In particular, the most prominent humanitarian crisis that this paper will deal with concerns the period of 1998- 1999. The Armed Forces of the government of Serbia might be classified in the ranks of “defensive realism”. The Kosovo Liberation Army (KLA) was struggling to protect the Albanian civilian population from the Milosevic regime, while Serbia was committed to preserving and attaining national security. In addition, there the principle of security dilemma because the KLA was declared a terrorist organization by state organs at that time. On the other hand, NATO’s intervention in Kosovo, even though it was missioned to protect human values, additionally aimed at its geopolitical and hegemonic strategies in the world of the anarchic international political system. Yet, in the theory of international relations, this can be classified as a form of offensive realism. This article consists of two main parts: The first part aims to research the position of classical realism regarding the conflict in Kosovo using the main principles as they are; survival, self-help, and security dilemma, and the position of neoclassical realism, which focuses more on state agents and domestic policy and the reflection of these state variables toward the impact on the construction of foreign policies. The second part of this study focuses on criticisms of the realist school’s criticism of NATO’s intervention in Kosovo. The main purpose of this article is to investigate the position of realism claiming that; the exclusive monopoly in the use of power belongs to states. In addition, this study aims to illuminate the criticisms that realism uses against foreign interference in domestic affairs. Yet, states are major actors in the anarchic global system that possesses a sole monopoly over their people and sovereignty. Any domestic disturbance and intervention from abroad is strongly condemned and violates the principle of non-interference in the internal affairs of other sovereign states.