The purpose of this study was to estimate child behavioral problems over time and determine gender differences in behavioral problems between children born to adolescent and adult mothers in Taiwan. The consistency between parent’s and teacher’s reports was also examined. Secondary analysis of a longitudinal dataset from Taiwan was conducted. A matched sample of 107 children born to adolescent mothers and 111 children born to adult mothers were recruited. Child behavioral problems were assessed by parents at Time 1 (1st and 2nd grades) and by teachers at both Time 1 and Time 2 (5th and 6th grades). Generalized estimating equations and paired t-test were used. At Time 1, compared to children of adult mothers, children of adolescent mothers had had more behavioral problems by both parental and teacher’s reports. Both parents and teachers reported that boys had more behavioral problems than girls. Moreover, according to teacher reports, children of adolescent mothers and boys had more behavioral problems and these differences persisted over time, even controlling for sociodemographic characteristics. In addition, parents reported higher scores of behavioral problems than teachers. In conclusion, child behavioral problems in Taiwan are associated with maternal age at child birth and child’s gender. Interventions may profitably focus on determining the mechanisms that lead to behavior problems in children of adolescent mothers, and/or reducing adolescent pregnancy as a way of decreasing child behavioral problems. Screening and preventive interventions for child behavior problems may need to be gender-specific.