Objective: Implementation science is an emerging area in physical activity (PA) research. We sought to establish the current state of the evidence related to implementation of school-based PA models to explore 1) the relationship between implementation and health outcomes, and 2) factors that influence implementation. Methods: We searched 7 electronic databases (1995-2014) and included controlled studies of school-based PA programmes for healthy youth (6-18 y) measuring at least one physical health-related outcome. For objective 1, studies linked implementation level to student-level health outcome(s). For objective 2, studies reported factors associated with implementation. Results: There was substantial variability in how health outcomes and implementation were assessed. Few studies linked implementation and health outcomes (n=15 interventions). Most (11/15) reported a positive relationship between implementation and at least one health outcome. Implementation factors were reported in 29 interventions. Of 22 unique categories, time was the most prevalent influencing factor followed by resource availability/quality and supportive school climate. Conclusions: Implementation evaluation supports scale-up of effective school-based PA interventions and thus population-level change. Our review serves as a call to action to 1) address the link between implementation and outcome within the school-based PA literature and 2) improve and standardize definitions and measurement of implementation.