Purpose: The purpose of this study was to perform a systematic review to assess current evidence for association between various risk factors and the prevalence or incidence of early childhood caries (ECC). Methods: Two reviewers searched various databases until January 2019. The Newcastle-Ottawa scale was used to perform risk of bias assessment. The included studies were categorized according to the World Bank classification. Data were summarized in a meta-analysis using fixed and random effects inverse-generic meta-analyses. Results: A total of 7,034 records involving 89 studies that evaluated 1,352,097 individuals were included; 23 were high, 46 were moderate, and 20 were of low quality. A total of 123 risk factors were found. Meta-analysis revealed that the strongest risk factors found in the high-income countries were presence of dentinal caries (dmft greater than zero; odds ratio [OR] equals 4.21 [2.18 to 8.16]) and high levels of mutans streptococci (OR equals 3.83 [1.81 to 8.09]). In upper-middle-income countries, presence of enamel defects (OR equals 14.62 [6.10 to 35.03]) was found to be the strongest risk factor. Conclusion: The strongest risk factors associated with early childhood caries was the presence of enamel defects, presence of dentinal caries and high levels of mutans streptococci.