Objective: To examine the efficacy of a Cognitive-Functional (Cog-Fun) intervention for children with ADHD. Method: Random allocation of 107 children to study or control groups preceded 10 parent–child weekly Cog-Fun sessions emphasizing executive strategy training in games and daily activities. Controls received treatment after crossover. Study participants were followed up 3 months post-treatment. Outcomes included parent/teacher ratings of executive functions, ADHD symptoms, and parent ratings of quality of life. Results: Eight children withdrew prior to treatment. All children in both groups who began treatment completed it. Mixed effects ANOVA revealed significant Time x Group interaction effects on all parent-reported outcomes. Treatment effects were moderate to large, replicated after crossover in the control group and not moderated by medication. Parent-reported treatment gains in the study group were maintained at follow-up. No significant Time x Group interaction effects were found on teacher outcomes. Conclusion: Cog-Fun occupational therapy (OT) intervention shows positive context-specific effects on parent, but not teacher, ratings.