Antisocial behaviors are common in adolescence. Family centred school-based interventions are attractive models for assisting adolescent populations. This study evaluated the impact of a universal family intervention implemented in Australian schools, on adolescent antisocial behavior. Year 7 students (57% female; M = 12.3 years, the first year of secondary school) in 12 randomly assigned schools, completed a survey in 2004 and were longitudinally followed in 2005 (n = 2042). Multivariate regression analysis revealed that exposure to the intervention did not significantly predict reductions in antisocial behavior across the whole-school population. However, significantly lower increases were evident for the sub-group of adolescents whose parents attended the parent-education activities. Given that 13% of intervention families attended the parent education events, future research should aim to increase parent attendance in school-based interventions.