BACKGROUND: The prevalence of childhood overweight has increased by approximately 50% in the past three decades, becoming a major public health concern worldwide. In Chile, an upper middle-income country, about 38% of children between two and four years of age are overweight, almost double the average in Latin America and the Caribbean. Various environmental and individual factors, and their interactions, affect childhood weight. Emerging evidence suggests childcare may also matter. Because the public provision of centre-based care is growing, childcare may be a useful policy tool to help prevent childhood overweight. METHODS: Using a nationally representative longitudinal survey of ~ 15 000 children in Chile (2010 and 2012), we estimated whether the type of child care (centre-based or maternal) a child attended at age 24 to 36 months was a significant predictor of the child's sex-and-age-specific body-mass-index (BMI) at age 36-48 months. We restricted our sample to children in full-time maternal care at baseline (12-24 months of age; n = 1273), but tested the robustness of results with the full sample. We compared children in centre-based care and in maternal care using difference-in-difference estimators and propensity score matching, and adjusted our estimates using child, family, and neighborhood characteristics. RESULTS: Children attending centre-based care had 0.27 SD lower BMI than children in maternal care at follow-up (P < 0.05). We found suggestive evidence this association may be modulated by the child's socioeconomic status and by how frequently the child watched television: we found smaller BMI changes for children at the bottom 80% of socioeconomic status (P < 0.05) and also for children who frequently watched television (P < 0.10). Our results were robust to various model specifications. CONCLUSIONS: Our findings suggest centre-based care programs, with adequate regulation and enforcement, may be a useful support to help curb the early childhood overweight epidemic, in addition to known effects in labor supply and child development.