OBJECTIVES : The aim of this systematic review and meta-analysis was to investigate the association between early antibiotic exposure and the risk of childhood obesity. METHODS : PubMed, EMBASE, Ovid, and the Research Information Sharing Service, a Korean bibliographic database, were systematically screened by keyword searching. The data that can be converted to log odds ratio (OR) were extracted from each study and pooled adjusted ORs with 95% confidence intervals (CI) were calculated by meta-analysis. RESULTS : A total of 12 studies including 5 cohort studies, 5 nested case-control studies, and 2 cross-sectional studies were systematically evaluated. Of those, 7 studies representing 44,517 participants were included in the meta-analysis. The antibiotic exposure at least once from birth to 24 months was associated with a significantly increased risk of obesity in childhood (adjusted OR, 1.16; 95% CI, 1.003-1.341). The effect was increased with repeated antibiotic exposures (4 or more repeated exposures, adjusted OR, 1.294; 95% CI, 1.154-1.452). The age at first antibiotic exposure before 6 months of life was associated with a significantly increased risk of obesity (adjusted OR, 1.275; 95% CI, 1.154-1.408). The association was not significant in children whose first exposure occurred 6 months after their births. CONCLUSIONS : Findings from the meta-analysis indicated that early-life antibiotic exposure and the repeated exposure were significantly associated with increased risks of childhood obesity. Future studies are needed to elucidate the mechanism of the association and to better estimate its clinical implications to proper antibiotic use in young children.