There is growing interest in the use of a multi-tiered system of supports framework to address issues related to school climate and bullying. Positive Behavioral Interventions and Supports (PBIS) is one such model that has received considerable attention; however, nearly all of the extant literature has focused on elementary and middle schools, with limited research on high schools. Furthermore, research on PBIS implementation in high schools, particularly in relation to school context, is scant. The current article examined the adoption and implementation of PBIS in 31 high schools randomly assigned to implement PBIS, within the context of a larger 58 high school randomized trial. We first present descriptive data on the rollout of the core features of PBIS, as measured by a set of research-based implementation tools administered by outside observers. We then explore the extent to which baseline rates of bullying and other school-level indicators of disorder were associated with the adoption of the multi-tiered PBIS framework over the course of 2 years. Multilevel analyses on the longitudinal implementation data indicated that schools with higher baseline rates of bullying generally implemented PBIS with greater fidelity over time. This suggests that schools with increased bullying may be particularly motivated to adopt PBIS. However, other baseline indicators of disorder were generally not associated with PBIS implementation and thus do not appear to be barriers to adoption. Implications for implementation research and practice in high schools are discussed.