IMPORTANCE: Although benefits have been reported for most exercise modalities, the most effective exercise approaches for reducing insulin resistance in children and adolescents with excess weight and the optimal exercise dose remain unknown. OBJECTIVE: To compare exercise training modalities and their association with changes in insulin resistance markers among children and adolescents with excess weight and to establish the optimal exercise dose. DATA SOURCES: For this systematic review and network meta-analysis, 6 electronic databases (PubMed, EMBASE, Cochrane Central Register of Controlled Trials, Scopus, Web of Science, and CINAHL) were searched for studies from inception to April 1, 2023. STUDY SELECTION: Randomized clinical trials (ie, randomized controlled trials and randomized trials without a control group) were included if they reported outcomes associated with aerobic training, resistance training, high-intensity interval training (HIIT), or a combination of these interventions. DATA EXTRACTION AND SYNTHESIS: Data extraction for this systematic review was conducted following a network meta-analysis extension of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guideline. Effect sizes were calculated as the mean difference (MD) with 95% CI using random-effects inverse-variance models with the Hartung-Knapp-Sidik-Jonkman method. The hierarchy of competing interventions was defined using the surface under the cumulative ranking curve. The Cochrane Risk-of-Bias tool, version 2 (RoB2), was used to independently assess the risk of bias of the included studies. The certainty of evidence in consistent networks was assessed using the Grading of Recommendation, Assessment, Development and Evaluation approach. The study protocol was prospectively registered with PROSPERO. Data analyses were conducted between May and June 2023. MAIN OUTCOMES AND MEASURES: The primary outcomes were fasting glucose, insulin, and homeostatic model assessment for insulin resistance (HOMA-IR). RESULTS: This analysis included 55 studies with a total of 3051 children and adolescents (mean [SD] age, 13.5 [2.3] years; 1537 girls [50.4%] and 1514 boys [49.6%]). Exercise was associated with reductions in fasting insulin (MD, -4.38 μU/mL [95% CI, -5.94 to -2.82 μU/mL]) and HOMA-IR (MD, -0.87 [95% CI, -1.20 to -0.53]). A nonlinear association in both markers was observed, with a required minimal exercise dosage of approximately 900 to 1200 metabolic equivalent of task minutes per week, especially in children and adolescents with insulin resistance at baseline. Combination HIIT and resistance training and concurrent training were the most effective approaches for reducing insulin resistance markers. On average, the certainty of evidence varied from low to moderate. CONCLUSIONS AND RELEVANCE: These findings underscore the role of exercise interventions in enhancing insulin resistance markers among children and adolescents with overweight and obesity. It is advisable to include resistance exercises alongside aerobic and HIIT programs for a minimum of two to three 60-minute sessions per week.