OBJECTIVES: This study was conducted to perform an effect size analysis of psychosocial interventions for internet addiction and to identify the intervention moderators applied to school-aged children. METHODS: For the meta-analysis, studies were included that were published in English or Korean until January 2015, without limitation in terms of the year. They were retrieved from 11 electronic databases and by manual searches according to predefined inclusion criteria. RESULTS: A total of 37 studies were selected, which included 11 treatment conditions and covered a total of 1,490 participants. The effect size estimates showed that psychosocial interventions had a large effect for reducing internet addiction (standardized mean difference [SMD], -1.19; 95% confidence interval [CI], -1.52 to -0.87) and improving self-control (SMD, 0.29; 95% CI, 0.11 to 0.47) and self-esteem (mean difference, 3.58; 95% CI, 2.03 to 5.12). The moderator analyses reveals that group treatments, a selective approach, a long duration, a community setting, or higher school grade had a larger effect. CONCLUSIONS: The findings of this review suggest that psychosocial intervention may be used to prevent Internet addiction in school-aged children, although further research should be conducted using a randomized controlled trial design or diverse age groups to provide evidence-based recommendations.