The objective was to quantify mothers’ misclassification of pre-school children’s weight status and to determine factors associated with such misperception. Almost 38% of 2287 mothers underestimated their child’s weight status. The frequency of underestimation was very high among ‘at risk of being overweight’ and ‘overweight’ children (88.3 % and 54.5 %, respectively). Given that mother’s weight perception might be an important determinant of child’s body weight development, clinicians and health professionals should help mothers correctly classify their children’s weight status, which could potentially help in the early prevention of overweight and obesity.