Saudi Arabia's foreign policy against the Islamic Republic of Iran (IRI) as the dependent variable is affected by the factors and elements of domestic level and also by the factors and elements of macro structural level as independent variables. Meanwhile, the present study aims at clarifying the dialectics of structural factors (regional-international developments) and those at agent level (Saudi Arabia's domestic developments) in shaping the Saudi Arabia's foreign policy against Iran. The present study, by means of structure-agent approach, seeks to explore the roots of shaping Saudi Arabia's aggressive foreign policy against the IRI in the interval of 2011-2013 and the concerned signals and proofs of the Saudi behavior as a question. The outcome of the present study suggests that the developments at the macro-structural level such as the international anarchy, the change of US strategy as a superpower, change in the order and balance between and among the regional powers after the Arabian uprisings of 2011 along with change at Saudi agent level, i. e. the rise of Mohammad bin Salman's team as the offensive elites, led to the shaping of Saudi Arabia's aggressive foreign policy against Iran in 2011-2018. Admittedly, these developments at the macro-structural level along with the domestic ones in Saudi Arabia resulted in shaping Saudi’ s aggressive behavior against Iran in a bilateral dialectical equation. In the same vein, the proofs of this behavior against Iran at the two levels of structure and agent include the creation of military-security coalition, establishment of amicable relations with Israel, exertion of institutional pressures, economic war, media-propaganda war and endeavor to exacerbate Iran's home unrests.