The present study investigated the mechanisms through which a parenting intervention for military families fosters positive peer adjustment in children. A sample of 336 families with a history of parental deployment enrolled in a randomized controlled trial of the After Deployment Adaptive Parenting Tools (ADAPT) preventive intervention. ADAPT is a 14-week preventive intervention designed to strengthen parenting in military families. The intervention was associated with improvements in mother’s and father’s parental locus of control (i.e., a more internal locus of control) at a 6-month follow-up assessment while controlling for baseline levels. Mothers’ parental locus of control was positively associated with improvements in children’s peer adjustment 12 months following the intervention while controlling for baseline peer adjustment. A significant indirect effect revealed that participation in ADAPT resulted in improved 12-month peer adjustment by improving mothers’ parental locus of control. Implications for supporting youth resilience to stressors associated with deployment are discussed.