The civil war in Syria lasts over two years and its progressing escalation indicates that its quick solution is far from being feasible. It causes numerous repercussions not only for Syria itself – by war damage and erosion of the social fabric, but also for the Middle East, especially due to direct involvement of regional actors in the conflict. Particularly vulnerable is the Hashemite Kingdom of Jordan to which Syrian war constitutes a major security threat, probably the biggest one Jordan has to face in more than 40 years. The article presents the monarchy’s reaction towards the Syrian crisis and accordingly analyzes the security system of Jordan by indicating complexity and multidimensionality of threats inflicted by the war in Syria by applying the comprehensive security approach. Intensification of the military activity on ground, deteriorating humanitarian situation of the civilians and their massive influx into Jordan, a direct military threat and several dangers related to uncertain future of Syria and overload of Jordanian socio-economic system are indicated as key factors endangering the very existence and stability of the monarchy.