The aim of this study was to examine which aspects related to fathering and the father-child relationship are affected by the Family Communication Project (FCP), and whether changes in destructiveness explain the intervention's effects on father-child attachment and fathering. Prior evaluation studies have suggested that fathering and the father-child relationship may be particularly vulnerable to the effects of destructive conflict, and, as such, most amenable to interventions targeted toward reducing destructiveness and toward improving fathering and the father-child relationship. The results of the father model revealed that those in the PA condition had significantly higher attachment to fathers at posttest than the control. With respect to destructiveness, those in the PO condition had significantly more changes in destructiveness over time than the control. Neither the PA nor PO condition had any mediated effect of on fathering or attachment via destructiveness. The results of the mother model did not reveal any significant effects (direct or mediated) of the intervention. Thus, the intervention effects were unique to the father model, suggesting support for fathering vulnerability.