There is growing support for the efficacy of mindfulness training with parents as an intervention technique to improve parenting skills and reduce risk for youth problem behaviors. The evidence, however, has been limited to small scale studies, many with methodological shortcomings. This study sought to integrate mindfulness training with parents into the Strengthening Families Program: For Parents and Youth 10-14 (SFP 10-14), an empirically-validated family-based preventive intervention. It used a randomized-controlled comparative effectiveness study design (N = 432 families, 31% racial/ethnic minority) to test the efficacy of the Mindfulness-Enhanced Strengthening Families Program (MSFP), compared to standard SFP 10-14 and a minimal-treatment home study control condition. Results indicated that, in general, MSFP was as effective as SFP 10-14 in improving multiple dimensions of parenting, including interpersonal mindfulness in parenting, parent-youth relationship quality, youth behavior management, and parent well-being, according to both parent and youth reports at both postintervention and 1-year follow-up. This study also found that in some areas MSFP boosted and better sustained the effects of SFP 10-14, especially for fathers. Although the pattern of effects was not as uniform as hypothesized, this study provides intriguing evidence for the unique contribution of mindfulness activities to standard parent training.