There is a paucity of research considering the effect of behavioral family intervention (BFI) on parenting knowledge and the relative importance of both knowledge and parent confidence in reducing parenting dysfunction and problematic child behavior is unclear. In this study ninety-one parents (44 mothers, 47 fathers) of children aged 2-10 years completed an evidence-based BFI and were assessed at pre and post-intervention on knowledge of effective parenting strategies, parenting confidence, parent dysfunction, and reported intensity of externalised child behavior. Results showed that at pre-intervention parents higher in education (N = 57) demonstrated greater knowledge than those lower in education (N = 34). Relative to baseline, parents in both groups significantly improved their knowledge and confidence, reduced their dysfunction and reported less externalised child behavior. Effect sizes for the latter two variables were similar for both groups, however for parents higher in education the effect for confidence was larger than knowledge. Change in level of dysfunction explained the largest amount of unique variance in change to externalised child behavior. Results suggest that for optimal outcomes for parenting and child behavior management more knowledgeable parents may benefit from interventions that focus on practice and consolidation of already learned skills in order to increase confidence whereas for less knowledgeable parents the teaching of new skills and strategies, alongside increasing confidence, are important.