There are a variety of complex and dynamic factors that shape foreign policy orientations. Among these factors, perceptions/misperceptions about national interests along with geopolitical position have essential roles in shaping foreign policy. This article examines how the geopolitics of Lebanon shaped Syria's foreign policy towards Lebanon during 1975-1990 Civil War in Lebanon. It maintains that the Lebanese Civil War jeopardized Syria's national interests, while it accorded Syria a unique venue to influence domestic and regional issues. Lebanon’s position in the Arab-Israeli conflict, particularly the presences of tens of thousands of Palestinian refugees, led Israel to invade Lebanon in order to dismantle Palestinian armed groups. Subsequently, the interventions of both regional and international powers in Lebanon became Lebanon’s prime geopolitical significance, which forced Syria to intervene militarily in Lebanon in order to maintain Syrian national interests.