Objectives: This systematic review aimed to identify perinatal risk factors associated withobesity in children aged ≤5 years. Methods: This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Medline (via PubMed), Embase, and Cochrane CENTRAL were searched from inception, without language or date restrictions. In addition, gray literature sources, including LILACS and CNKI, were screened for comprehensive evidence synthesis. Metaanalyses were conducted to estimate pooled risk ratios. Study quality was independently assessed by 2 reviewers using the Joanna Briggs Institute critical appraisal tool. Results: A total of 24,643 articles were screened, and 39 cohort studies were included in the final analysis. Sample sizes ranged from 169 to 333,353 participants. Meta-analysis results indicated that high gestational weight gain (adjusted risk ratio [aRR], 1.46; 95% confidence interval [CI], 1.17–1.82), history of cesarean section (aRR, 1.25; 95% CI, 1.17–1.33), macrosomia (aRR, 1.88; 95% CI, 1.55–2.27), antibiotic use (aRR, 1.31; 95% CI, 1.14–1.51), pre-pregnancy obesity (aRR, 1.82; 95% CI, 1.21–2.73), and female sex (aRR, 1.46; 95% CI, 1.32–1.61) were associated with an increased risk of obesity in children aged ≤5 years. Exclusive breastfeeding (aRR, 0.74; 95% CI, 0.64–0.85) was identified as a protective factor. Conclusion Perinatal factors and pre-pregnancy obesity played important roles in increasingthe risk of obesity in children aged ≤5 years. Breastfeeding was associated with a protective effect against childhood obesity. Therefore, obesity prevention efforts should begin during pregnancy, and maintaining appropriate maternal weight before conception is equally essential.