Recent research in implementation science has focused on identifying factors that predict adoption of evidence-based practices in schools. Less attention has focused on examining the adoption of practices within districts. This study included a sequential cohort of 552 districts in 25 U.S. states adopting an evidence-based framework, school-wide positive behavioral interventions and supports (PBIS). We examined schools within districts reporting on PBIS fidelity during their first five years of PBIS initiatives. Latent change score and multi-level growth modeling were used to examine and predict the percent of district adoption of PBIS over time. Results showed a significant increase in the rate of district adoption over the first 4 years of the initiative, with a decrease in growth between years 4 and 5. District size, proportion of students receiving free or reduced lunch, and districts located in cities and towns were found to be significant predictors of the percent of schools adopting PBIS. Implications for future implementation research and strategies for increasing the adoption of PBIS are discussed. [This paper was published in "Journal of School Psychology" v76 p159-167 2019.]