OBJECTIVE. To test functional improvement after a group cognitive-functional occupational therapy intervention for preschoolers with attention deficit hyperactivity disorder (ADHD). METHOD. Seventeen preschooler-parent dyads attended 11 weekly group sessions focused on acquiring executive strategies through occupational performance. Functional improvement was measured using the Canadian Occupational Performance Measure (COPM) and Goal Attainment Scaling (GAS); executive function, using the Behavior Rating Inventory of Executive Function-Pediatric; ADHD symptomatology, using Conners' Parent Rating Scale-Revised and Conners' Teacher Rating Scale-Revised; and social functioning, using the Social Participation scale of the Sensory Processing Measure. RESULTS. Significant improvement was found on the COPM and GAS measures, whereas mixed results were found on the other measures, with improvements found in children whose scores indicated impairment at baseline. CONCLUSIONS. Cognitive-functional group intervention appears to significantly improve daily functioning, executive function, and social functioning for children who demonstrate clinical impairment. Further research with a larger sample, a control group, and follow-up is required.