Children with Down syndrome may be at increased risk of problems associated with inactivity. Early intervention to increase physical activity may lead to increased participation in typical activities and long-term increases in quality of life (e.g., decreased likelihood of obesity-related illness). A multi-component intervention, including video modeling, prompting, and behavior-specific praise, was implemented to increase the physical activity behaviors of three young children with Down syndrome on a typical preschool playground. Results, evaluated in the context of an A-B-A-B withdrawal design, showed increases in moderate-to-vigorous physical activity (MVPA) for all children during intervention conditions. To evaluate social validity of behavior changes, average data values in each condition were graphed alongside normative comparison data of typically developing peers, showing that average MVPA for participants during intervention conditions was lower than average peer values but was within the range demonstrated by peers.