In this study, we examined parenting practices as mediators of changes in child conduct problems in ethnic minority families participating in Parent Management Training—Oregon Model (PMTO). The participants included 96 Somali and Pakistani immigrant mothers and their children living in Norway. The families were randomized to PMTO or a waiting-list control group. Self-report assessments were made at baseline and after the intervention using standardized measures. A path model suggested that improvements in the child conduct problems were fully mediated by a reduction in harsh maternal discipline and an increase in positive parenting. When the mediation pathways were tested separately, both the reduction in harsh discipline and the increased positive parenting functioned as mediators of the reduction in child conduct problems. These findings emphasize the importance of including components that address the parent's use of both harsh and positive parenting practices when implementing parenting training among ethnic minority families.