PurposeParents’ underestimation of young children’s weight can reduce their engagement and readiness to implement changes in children’s diet and physical activity. Childcare teachers can support parents’ identification of children at risk for being overweight only if they can accurately do this themselves.DesignQuantitative, cross-sectional study.SettingFifteen kindergartens near Lisbon, Portugal.Subjects319 parents, 32 teachers (47.5% and 100% response rate, respectively), and 319 children.MeasuresCaregivers classified the children’s weight, considering their height and age as underweight, healthy weight, or overweight; children’s body mass index (BMI) status for age and sex was assessed.AnalysisDifferences in caregivers’ accuracy of children’s weight perception were assessed. Multilevel multivariate logistic regression models were used to analyze the predictors of the accuracy of teachers’ and parents’ weight perception as a binary outcome.ResultsThe proportion of children with overweight correctly assessed differed significantly (P= 0.004) between teachers (31.1%) and parents (17.5%). The child’s BMI percentile was the only significant positive predictor for both caregivers’ weight perception accuracy (P< 0.001 andP= 0.004, for parents and teachers, respectively), holding the child’s age and sex constant.ConclusionAlthough childcare teachers were better raters than parents when evaluating children’s weight status, the percentage of children with overweight that childcare teachers misclassified was still relatively high.