Generalised anxiety disorder (GAD) is the most significant and common of the anxiety disorders. Intolerance of uncertainty (IU) and negative metacognitive beliefs are two prominent cognitive factors in models of GAD, however only one study to date has examined the relative contribution of these factors. Therefore, this study aimed to investigate and compare these cognitive factors in their prediction of GAD symptoms, and also to examine possible developmental influences on GAD by examining the link between symptoms and the parentification style of childrearing. In this analogue study, 119 non-clinical participants (M age 22.90 years; 95 females, 24 males) completed measures of these constructs. Results indicated that both IU and negative beliefs about worry significantly related to GAD symptoms, however, the degree to which they predicted GAD symptoms did not significantly differ. Although a weak but significant relationship was found between parentification and GAD, this relationship did not remain significant after controlling for depression. Implications and limitations are discussed. (Contains 2 tables.)