Cognitive behavioral therapy (CBT) has received considerable empirical support for internalizing disorders including anxiety, depression, obsessive-compulsive disorder, and post-traumatic stress disorder in children and adolescents. However, there is less knowledge regarding how CBT performs when delivered in routine clinical care. A systematic review and meta-analysis was conducted of CBT for internalizing disorders in children and adolescents in routine clinical care. Ovid MEDLINE, Embase OVID, and PsycINFO were systematically searched for articles published until October 2019. The effectiveness of CBT, methodological quality, and moderators of treatment outcome were examined. The effects of CBT in routine clinical care were benchmarked by comparing with efficacy studies for the same disorders. Fifty-eight studies were included, comprising 4618 participants. Large effect sizes for outcome were detected at post-treatment (g = 1.28–2.54), and follow-up (g = 1.72–3.36). Remission rates across diagnoses ranged from 50.7% - 77.4% post-treatment, to 53.5% -83.3% at follow-up. Attrition rate across the disorders was 12.2%. Quality of the included studies was fair, and heterogeneity was high. Similarities between the effectiveness and efficacy studies were greater than the differences in outcome. CBT delivered in routine clinical care is efficacious in reducing internalizing disorders and symptoms. The outcomes are comparable with results obtained in efficacy studies.