OBJECTIVE To summarize the efficacy of metformin in reducing BMI and cardiometabolic risk in obese children and adolescents without diabetes. RESEARCH DESIGN AND METHODS We performed a systematic review and meta-analysis of randomized controlled trials (RCTs). Double-blind RCTs of ≥6 months duration in obese subjects age ≤19 years without diabetes were included. Our primary outcomes of interest include changes in BMI and measures of insulin sensitivity. RESULTS Five trials met inclusion criteria (n = 320 individuals). Compared with placebo, metformin reduced BMI by 1.42 kg/m2 (95% CI 0.83–2.02) and homeostasis model assessment insulin of resistance (HOMA-IR) score by 2.01 (95% CI 0.75–3.26). CONCLUSIONS Metformin appears to be moderately efficacious in reducing BMI and insulin resistance in hyperinsulinemic obese children and adolescents in the short term. Larger, longer-term studies in different populations are needed to establish its role in the treatment of overweight children.