A number of Western theorists in the field of security policy have regarded the national security policy of the Islamic Republic of Iran as "breaking the rules of the game" and threatening other countries. Iranian officials, in response, have argued that, contrary to such prevalent images and perceptions, the Islamic Republic not only does not pose any threats to the region and the world but instead it has played a "pacifying" role in its surrounding tense environment. This article aims at examining the salient aspects of Iran’s national security policy. More specifically, it seeks to answer the following questions: What are   the goals and behavior of Iran’s foreign and defense security policies? Has Iran's defense policy been defensive or aggressive/expansionist? Which security threats are perceived in Iran's defense policy at the regional and international levels? And what are the most appropriate and effective foreign policy tools for responding to these security threats? Having reviewed Iran’s security threats and opportunities, and the policies pursued to enhance its status in the region and in the world system, the article has come to the conclusion that recent changes in the regional security environment as well as the new U.S. security strategies have had negative impact on Iran's national security.