The occurrence of the Islamic revolution in Iran in 1979 followed by a broad "institutionalization" of political power, led to some unique consequences with regard to the domestic and, more importantly, the international politics of the country. Iran was, as a result, suddenly transformed to an independent, proactively religious power in the region. The impacts on Iran's security decision-making process have been one of the most challenging controversies in foreign policy analysis and security studies. This paper attempts to explore in evolution of Iran's security structure and the extent to which the bureaucratic structures impact the actual process of security-related policy-making. It investigates the role of the revolution on the Iranian security complex and associated institutions. Moreover, it will aim to explore the dynamics related to the formation of institutions --what structures were established, To what extend the formation and evolution of institutions and councils affect the security policy-making? Although "formal" security policy-making process is still largely in the exclusive domain of the Supreme leader, this paper argues that the Iran-Iraq war has considerably affected the engagement of institutions and organizations in security related policy-making structures in Iran. The approach to this analysis will be based on interviews, analysis of the content of available archives and discourse analysis. I will be choosing different security decision-making cases as examples. In order to assure that the argument in this respect provides a credible analysis, capturing factors leading to crisis decision-making, I will pick my cases from a combination of crisis decision-making in regional and international security terms together with cases assessed as being of low-risk but nonetheless invoking the same decision-making mechanisms. The paper thus argues that bureaucracies and institution have gained an important role in security policy-making structures in Iran, through "formal" and "informal" action channels. It concludes that the security related policies is tilting towards reflecting different organizational and strategic standpoints on each issue. Thus, the institutional and bureaucratic mechanisms have had an increasing role in shaping the security-related decisions.