Background <p>The use of probiotics/synbiotic to assist in the treatment of overweight/obese children is currently a hot topic. However, the therapeutic effect is controversial. This meta-analysis assesses their effects and safety in overweight/obese children.</p> Methods <p>PubMed, Cochrane, Web of Science, and Embase were searched (2000- April 2024) for RCTs on probiotics/synbiotics in overweight/obese children. Primary outcomes included anthropometric measures, lipid profiles, insulin sensitivity, inflammatory markers, and liver enzymes. Result stability and heterogeneity sources were assessed by sensitivity and subgroup analyses. Subgroup analyses were conducted based on age, intervention time, complications and treatment methods. Review Manager 5.4.1 and STATA 15.0 were used to conduct the statistical analysis.</p> Results <p>A total of 16 studies were included (<i>n</i> = 763). <i>L. acidophilus</i> is the most commonly used. We found significant reductions in BMI-z, CRP and TNF-α. Synbiotics/probiotics are more effective when the treatment lasted for more than 3 months or when the patients was under 12 years old. All indicators lost significance in patients with NAFLD.</p> Conclusions <p>Probiotics/synbiotics significantly improved BMI-z, CRP, and TNF-α in overweight/obese children. Patients without complications under the age of 12 or those whose treatment lasts for more than 3 months will gain more benefits.</p> Impact <p><UnorderedList Mark="Bullet"> <ItemContent> <p>This study found that probiotics/synbiotics could significantly improve BMI-Zscore, CRP, and TNF-α in overweight/obese children.</p> </ItemContent> <ItemContent> <p>This meta-analysis, incorporating the latest randomized controlled trials (RCTs), identified factors influencing probiotic/synbiotic efficacy through subgroup analysis: probiotic/synbiotic type, treatment duration, patient age, and the presence of complications.</p> </ItemContent> <ItemContent> <p>This study provides further evidence supporting the effectiveness of probiotics/synbiotics in treating overweight/obese children.</p> </ItemContent> </UnorderedList></p>