Previous research suggests the neighborhood environment may be an important influence on children’s physical activity (PA) behaviors; however, findings are inconsistent. The purpose of this study was to further understand the relationship between perceptions of the neighborhood environment and children’s afterschool moderate-to-vigorous PA. Utilizing a structural equation modeling technique, we tested a conceptual model linking parent and child perceptions of the neighborhood environment, parent support for PA, and child outdoor PA with children’s afterschool moderate-to vigorous PA. We found that child perception of the neighborhood environment and outdoor PA were positively associated with afterschool moderate-to-vigorous PA. In addition, parent support for PA positively influenced children’s outdoor PA. The neighborhood environment and outdoor activity appear to play an influential role on children’s afterschool PA behaviors.