It is well known that war has negative effects on the mental health of civilian populations. However, different perceptions and reactions to trauma have different impacts on the psychological well-being of affected populations. This study assessed the mental health status of adult internally displaced persons (IDPs) at an early stage of the summer 2006 war in Lebanon, and investigated the relationship between their mental status and socio-demographic determinants, and individual and collective experiences of the war. Two hundred and eighteen IDPs were surveyed for the prevalence and determinants of acute trauma symptoms. The reporting of anxiety symptoms was assessed using a version of the Hamilton Anxiety Rate Scale that was translated into Arabic. The prevalence of self-reported anxiety symptoms was relatively low, at 25.8%. After adjustment, the outcome variable was significantly associated with being female (OR=2.9), experiencing bombing while fleeing (OR=2.8) and being surveyed in days of bad political news (OR=2.7). Factors related to displacement circumstances and coping strategies showed no significance. This result suggests that individual and collective war experience had an equal importance in predicting anxiety. This study recommends the consideration of factors operating at a collective level for better understanding civilians' mental health in times of war.