To support school physical education, United States (US) national organizations in medicine, health, and education recommend that schools adopt comprehensive school physical activity programmes (CSPAPs). An important factor in successful CSPAP implementation is the involvement of the school principal. The purpose of this study was to examine relationships between principals’ self-reported CSPAP involvement and their social-ecological-based perceptions about CSPAPs. We analysed survey responses from a national sample of principals in the US who indicated their school had a CSPAP ( n = 198). Exploratory structural equation modelling supported a single-factor solution for CSPAP involvement (12 items) and three social-ecological factors, which we labelled ‘intrapersonal’ (nine items mainly focused on expected outcomes of CSPAPs), ‘interpersonal’ (five items focused on parents’ and teachers’ support of the CSPAP), and ‘environmental’ (12 items focused on the support of the overall school environment, the community surrounding the school, and public policy for the CSPAP). Path analysis showed involvement factor scores are predicted by intrapersonal factor scores, which, in turn, are predicted by interpersonal and environmental factor scores. The results of this study are helpful in identifying targets for future research and practice related to CSPAP implementation and can inform efforts to prepare and support principals with respect to their CSPAP involvement.