Background: The development of mindfulness parenting programs in recent years offers a promising direction for targeting parental emotional dysregulation in families of children with attention deficit hyperactivity disorder (ADHD). Nevertheless, research on the effectiveness of mindfulness parenting programs is limited, and little is known about the contribution of mindfulness skills to parenting when integrated with parent training (PT). Objective: The present study evaluated a mindfulness skills augmentation to PT for ADHD. We hypothesized that mindfulness-enhanced PT would improve parental emotion regulation and reduce hostile and coercive parenting. Method: We developed a 90-min mindfulness skills protocol and integrated it with a nonviolent resistance (NVR) PT program addressing ADHD and behavior difficulties. A total of 79 families were randomly assigned to PT or mindfulness-enhanced PT. Forty-three families completed intervention. We used multilevel modeling to evaluate parental emotion regulation, hostile and coercive parenting, and child behavioral symptoms across treatments and over time. Results: Across treatment conditions, mothers' negative feelings, escalating behaviors, and capacity for emotion regulation improved significantly following treatment. Fathers in the mindfulness condition reported greater improvement in the capacity for emotion regulation, reduced negative feelings, and reduced parental submission compared with fathers in the PT condition. We found no differences in child externalizing symptoms, which decreased significantly in both groups. Conclusions: Study results suggest that PT in NVR is effective in improving maternal capacity for emotion regulation and in reducing hostile and coercive parenting. For fathers, a mindfulness-based skills augmentation may be important for enhancing treatment benefits.