IntroductionThe prevalence of children with overweight and obesity is increasing worldwide. Multicomponent interventions incorporating diet, physical activity and behavioural change have shown limited improvement to body mass index (BMI). However, the impact of psychotherapy is poorly explored. This systematic review aims to assess the effects of psychotherapeutic approaches for children with all degrees of overweight.Methods and analysisWe will include randomised clinical trials involving children and adolescents between 0 and 18 years with overweight and obesity, irrespective of publication type, year, status or language up to April 2020. Psychotherapy will be compared with no intervention; wait list control; treatment as usual; sham psychotherapy or pharmaceutical placebo. The following databases will be searched: Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, MEDLINE, Embase, PsycINFO, PubMed, Web of Science, CINAHL and LILACS. Primary outcomes will be BMI z-score, quality of life measured by a validated scale and proportion of patients with serious adverse events. Secondary outcomes will be body weight, self-esteem, anxiety, depression and proportion of patients with non-serious adverse events. Exploratory outcomes will be body fat, muscle mass and serious adverse events. Study inclusion, data extraction and bias risk assessments will be conducted independently by at least two authors. We will assess risk of bias according to Cochrane guidelines and the Cochrane Effective Practice and Organisation of Care guidance. We will use meta-analysis and control risks of random errors with Trial Sequential Analysis. The quality of the evidence will be assessed using Grading of Recommendations Assessment, Development and Evaluation Tool. The systematic review will be reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Cochrane guidelines.Ethics and disseminationAs individual patient data will not be included, we do not require ethics approval. This review will be published in a peer review journal.PROSPERO registration numberCRD42018086458.