Positive Behavioral Interventions and Supports (PBIS) is a universal, school-wide prevention strategy that is currently implemented in over 7,500 schools to reduce disruptive behavior problems. The present study examines the impact of PBIS on staff reports of school organizational health using data from a group-randomized controlled effectiveness trial of PBIS conducted in 37 elementary schools. Longitudinal multilevel analyses on data from 2,596 staff revealed a significant effect of PBIS on the schools' overall organizational health, resource influence, staff affiliation, and academic emphasis over the 5-year trial; the effects on collegial leadership and institutional integrity were significant when implementation fidelity was included in the model. Trained schools that adopted PBIS the fastest tended to have higher levels of organizational health at baseline, but the later-implementing schools tended to experience the greatest improvements in organizational health after implementing PBIS. This study indicated that changes in school organizational health are important consequences of the PBIS whole-school prevention model, and may in turn be a potential contextual mediator of the effect of PBIS on student performance. (Published Abstract) 56 references