Syrian civil war that started in 2011 is characterized by an extremely high degree of internationalization. The country has become the focus for the different actors in the world and regional politics, as separate states and international governmental and nongovernmental organizations. In this sense neighboring (regional) countries, whose own security and stability directly depends on the situation in Syria, show the greatest interest and activity. The Syria’s civil war is seen as an internationalized intrastate conflict – an armed conflict between a government and a non-government party where the government side, the opposing side, or both sides, receive troop support from other governments that actively participate in the conflict. This article focuses on the interventions of regional actors in the conflict, especially the most powerful regional states (Iran, Turkey, Saudi Arabia). The intervention of regional powers in the Syria’s civil war can be explained by the combination of realist and constructivist approaches. In such an insecure region, all major states seek to maximize their power, famously creating a security dilemma, in which all end up less secure. Against this insecurity, all states “power balance”, in particular by forming alliances against shared threats. The inter-state rivalry for leadership of supra-state communities is endemic, expressed in recurring “cold wars”, in which stronger states deploy ideology and identity discourses to gain allies and subvert rival governments in the search for regional hegemony. Syria became a battleground in «proxy war», in which the warring parties actually serve the interests of their external patrons, who are fighting for regional leadership. Largely as a result of the internationalization of the conflict, Syria became a typical «fragile state» that will produce problems for a long time to come, even when the fighting finally stops: regional instability, refugees problem, criminal activities and extremism. Notwithstanding the Assad regime’s survival and clear victory in the civil war, the main regional interveners’ (Iran and Turkey) interference in Syria will continue, because threats to its national security and regional influence have not been completely eliminated.