Internet-delivered cognitive behavior therapy (ICBT) is a relatively novel treatment format with the potential to increase accessibility of evidence-based care. However, little is known about the feasibility and efficacy of ICBT in children and adolescents. We conducted a comprehensive systematic review and meta-analysis of ICBT for children and adolescents to provide an overview of the field and assess the efficacy of these interventions. A systematic literature search of six electronic databases was performed to identify ICBT intervention studies for children with a psychiatric condition, such as social anxiety disorder, or a somatic condition, such as chronic pain. Two reviewers independently rated study quality. Twenty-five studies, targeting 11 different disorders, were included in the review. Study quality and presentation of treatment variables, such as therapist time and treatment adherence, varied largely. Twenty-four studies (N=1882) were included in the meta-analysis and ICBT yielded moderate between-group effect sizes when compared with waitlist, g=0.62, 95% CI [0.41, 0.84]. The results suggest that CBT for psychiatric and somatic conditions in children and adolescents can be successfully adapted to an internet-delivered format.