© 2016 Kagawa et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Background/Objectives: Our objective was to explore the association between weight status and behavioral problems in children before school age. We examined whether the association between weight status and behavioral problems varied by age and sex. Subjects/Methods: This study used cross-sectional data from a nationally-representative sample of children and their families in Chile (N = 11,207). These children were selected using a cluster-stratified random sampling strategy. Data collection for this study took place in 2012 when the children were 1.5-6 years of age. We used multivariable analyses to examine the association between weight status and behavioral problems (assessed using the Child Behavior Checklist), while controlling for child's sex, indigenous status, birth weight, and months breastfed; primary caregiver's BMI and education level; and household wealth. Results: Approximately 24% of our sample was overweight or obese. Overweight or obese girls showed more behavioral problems than normal weight girls at age 6 (β = 0.270 SD, 95% CI = 0.047, 0.493, P = 0.018). Among boys age 1 to 5 years, overweight/obesity was associated with a small reduction in internalizing behaviors (β = -0.09 SD, 95% CI = -0.163, -0.006, P = 0.034). Conclusions: Our data suggest that the associations between weight status and behavioral problems vary across age and sex.