Objective: This study examined the effects of the OutSMARTers program on social skills, self-regulation, and executive functions compared with a Waitlist group and a parent training program. Method: Participants were 41 children with ADHD, aged 8 to 10 years. All groups were assessed with behavioral checklists and neuropsychological measures at baseline and post-treatment. The two treatment groups were reassessed with behavioral checklists after 3 months. Results: Findings revealed decreased ADHD symptoms, improved social skills, and better emotion regulation at post-treatment for the OutSMARTers compared with the Waitlist group on subjective measures. No differences were found on objective tasks or between the OutSMARTers and Parent groups after treatment but both treatment groups showed some improvement. In addition, most of the post-treatment changes were maintained for both groups 3 months later. Conclusion: The results indicate that the OutSMARTers program seems to benefit children with ADHD, but further research and treatment development is needed.