Objectives <p>To investigate risk factors for early childhood caries (ECC) among 1–2-year-old children in Beijing and to assess the effect modification of baseline caries experience on the associations between other risk factors and subsequent caries outcomes.</p> Methods <p>A 12–24-month prospective study was conducted from 2021 to 2023, a total of 919 participants with valid data were included in this study, with a follow-up rate of 76.9%. Oral health information and related factors were collected through parent-completed questionnaires and clinical dental examinations. Univariate analyses and a zero-inflated negative binomial (ZINB) regression model were used to identify risk factors.</p> Results <p>Caries incidence during follow-up was 29.8%, and the mean increase in decayed, missing, and filled primary teeth (Δdmft) was 0.94 ± 1.94. In the full-sample ZINB model, significant predictors of caries risk were frequency of snack intake, frequency of candy consumption, frequency of bedtime tooth brushing, frequency of&#xa0;bottle use at bedtime, and baseline caries status. In the baseline caries-free group, additional significant predictors of incident caries risk were parents’ caries status, frequency of saliva-sharing behavior, frequency of post-meal mouth rinsing, and the presence of additives in daily drinking water. Interaction analyses showed that the effects of parents’ caries status, saliva-sharing frequency, post-meal mouth rinsing frequency, presence of additives in daily drinking water, bedtime brushing frequency, and history of dental attendance on caries risk differed significantly between children with and without baseline caries.</p> Conclusion <p>The risk of early childhood caries (ECC) among 1–2-year-old children in Beijing was associated with multiple oral health-related factors. Baseline caries experience was a strong predictor of subsequent caries risk and significantly modified the effects of other risk factors.</p>