Abstract: Our objective was to determine age differences in the effects of a family-based intervention with 278 African American nonresident fathers and their 8 to 12-year-old sons. We assessed fathers' parenting, sons' perception of fathers' parenting, and sons' intentions to avoid violence (outcome) before and after the intervention. We first studied the mechanism of the effect with the complete sample of fathers and sons, and then on subsamples of fathers and younger (8-10 years) and older (11-12 years) children, using a multi-group structural equation modeling (SEM). In the pooled sample, the intervention enhanced fathers' parenting, which increased sons' perception of the fathers' parenting, resulting in sons' intentions to avoid violence in the future. Two age group differences were found: for younger sons, the intervention was effective on improving father's parenting, whereas for older sons, father's parenting had an effect on their son's perception of parenting. The findings of this study have practical implications for interventions with African American nonresident fathers, especially in terms of the timing and type of interventions offered.