Many afterschool physical activity programs and curricula are available, but evaluation of their effectiveness is needed. Well-marketed programs such as the Child and Adolescent Trial for Cardiovascular Health (CATCH) Kids Club have shown limited effectiveness in increasing physical activity for participants in comparison to control groups. However, other afterschool programs increased the amount of time children spent in physical activity by up to 17 percent. Effective strategies for increasing physical activity in afterschool programs include, for example, allocating time specifically for physical activity and providing professional development to help staff foster physical activity among youth and participate themselves in physical activity. To add to this discussion of the effectiveness of afterschool physical activity programs, the authors developed, implemented, and studied a physical activity program called Jumpin' Jaguars for elementary-aged children. This paper describes the implementation of Jumpin' Jaguars in one school, outlines findings on its physical activity outcomes, and offers recommendations, based on the findings, for improving physical activity levels in afterschool programs.