The aim of the study is to examine the relationships in between intolerance of uncertainty, perceived social support, insecure adult attachment (anxious and avoidant) and anxiety. The mediator effects of intolerance of uncertainty and perceived social support on the relationship between adult attachment and anxiety have not been examined together yet. Considering the prevalence of anxiety and the etiology of attachment, the outcomes of this study are important in both theoretical and practical contexts. Four hypotheses of the study are built on the assumption that both intolerance of uncertainty and perceived social support will have mediating effects on the relationships between anxious attachment and anxiety, and between avoidant attachment and anxiety. The sample consists of 880 university students between the ages of 18-25. Experiences in Close Relationships Inventory-II-Short Form, Trait Anxiety Form, Intolerance of Uncertainty Scale-Short Form and Multidimensional Perceived Social Support Scale were used. According to the findings, intolerance of uncertainty was found to be in the role of mediator on the relationship between anxious attachment and anxiety, but not on the relationship between avoidant attachment and anxiety. The family and significant other sub-dimensions of perceived social support mediated the relationship between both anxious attachment and anxiety, and avoidant attachment and anxiety.