Various Cognitive Behavioral Therapy (CBT) programs for externalizing disorders in children and adolescents are supported by a substantial body of empirical evidence. Most of the research evidence comes from efficacy studies conducted in university settings, but there is less knowledge about the effect of these treatments in routine clinical care. The purpose of this meta-analysis was to investigate the effectiveness of CBT in non-university settings for Attention Deficit Hyperactivity Disorder (ADHD), Conduct Disorder (CD) and Oppositional Defiant Disorder (ODD). Embase OVID, Ovid MEDLINE and PsycINFO were systematically searched for eligible studies published up to May 2020. In total, 51 treatment effectiveness studies involving 5295 patients were included. The average within-group effect size at post-treatment was significant (g = 0.91), and there were large effect sizes for both ADHD (g = 0.80) and CD/ODD (g = 0.98). At post treatment, remission rates were 38% for ADHD and 48% for CD/ODD, and the overall attrition rate was 14%. Benchmarking against efficacy studies showed that CBT in routine clinical care yields remission rates, within-group effect sizes and attrition rates that are very similar to those found in university settings. The findings support the transportability of CBT for externalizing disorders from university settings to routine clinical care. PROSPERO registration: CRD42020147524. Keywords: Children; Cognitive behavior therapy; Externalizing disorders; Meta-analysis; Routine care. Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.