Head Start centers were randomly assigned to intervention (parent training) or control conditions, and the role of maternal mental health risk factors on participation in and benefit from parent training was examined. Parenting was measured by parent report and independent observation in 3 domains: harsh/negative, supportive/positive, inconsistent/ineffective parenting. Structural equation modeling showed that parent engagement training was associated with improved parenting in a dose-response fashion. Mothers with mental health risk factors (i.e., depression, anger, history of abuse as a child, and substance abuse) exhibited poorer parenting than mothers without these risk factors. However, mothers with risk factors were engaged in and benefited from the parenting training program at levels that were comparable to mothers without these risk factors.