A meta-analysis of school-based interventions for anxious and depressed youth using QUORUM guidelines was conducted. Studies were located by searching electronic databases, manual effort, and contact with expert researchers. Analyses examined 63 studies with 8,225 participants receiving cognitive-behavioral therapy (CBT) and 6,986 in comparison conditions. Mean pre–post effect sizes indicate that anxiety-focused school-based CBT was moderately effective in reducing anxiety (Hedge's g = 0.501) and depression-focused school-based CBT was mildly effective in reducing depression (Hedge's g = 0.298) for youth receiving interventions as compared to those in anxiety intervention control conditions (Hedge's g = 0.193) and depression intervention controls (Hedge's g = 0.091). Predictors of outcome were explored. School-based CBT interventions for youth anxiety and for youth depression hold considerable promise, although investigation is still needed to identify features that optimize service delivery and outcome.