Background: Although worry is common in children, empirical models of worry remain largely untested in youth. A small number of studies have established preliminary links between cognitive variables and worry in children younger than 12 years old. These cognitive variables include positive and negative beliefs about worry, intolerance of uncertainty, and problem orientation. Aims: The current study examined these variables concurrently and their association with worry. We also examined the extent to which intolerance of uncertainty mediated the association between worry and beliefs about worry. Method: Eighty elementary school children aged 8 to 12 years completed a battery of self-report measures. Results: As a group, the cognitive variables significantly predicted worry scores; negative beliefs about worry was the only significant individual predictor. As a group, the four cognitive variables discriminated clinical from nonclinical levels of worry; positive beliefs about worry and intolerance of uncertainty were the only significant individual predictors. Finally, intolerance of uncertainty mediated the association between worry and both positive and negative beliefs about worry. Conclusions: Components of a cognitive model of worry are largely applicable to children. Negative beliefs about worry were associated with worry across the continuum, while intolerance of uncertainty and positive beliefs about worry were more strongly associated with clinical levels of worry. Intolerance of uncertainty accounted for a significant portion of the association between metacognition and worry and may be a particularly effective target for treatment. Further implications for conceptual models and treatment interventions are discussed.