This study examined the relation between parental coping styles, discipline, and child behavior before and after participating in a parent training program for parents of children with Attention-Deficit/Hyperactivity Disorder (ADHD) and oppositional behavior. For mothers, use of more maladaptive and less adaptive coping styles was related to more self-reported lax and overreactive discipline, more observed coercive parenting, and more observed child misbehavior prior to parent training. No significant relations were found for mothers following parent training after controlling for pretreatment variables. For fathers, use of more maladaptive and less adaptive coping styles was related to self-reported lax discipline before and after parent training. Contrary to prediction, fathers who reported less seeking support and adaptive-focused coping showed the most improvement in their children's behavior. Most results remained significant after controlling for self-reported depression. Implications for improving parent training research and programs were discussed.