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 (MVPA). 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 MVPA. We found that child perception of the neighborhood environment and outdoor PA were positively associated with afterschool MVPA. 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.