The current study explored the extent to which a common measure of perceived implementation of critical features of Positive Behavioral Interventions and Supports (PBIS) predicted fidelity of implementation 3 years later. Respondents included school personnel from 261 schools across the United States implementing PBIS. School teams completed the Positive Behavioral Interventions and Supports Self-Assessment Survey to self-assess fidelity of implementation in different PBIS settings (school-wide, nonclassroom, classroom, individual). These scores were then analyzed to assess whether certain items predicted the fidelity of PBIS implementation, as assessed through another fidelity of implementation measure, the School-Wide Benchmarks of Quality, 3 years later. Regression analyses indicated that self-reported fidelity of implementation of Classrooms Systems significantly predicted sustained implementation and student outcomes, as assessed through levels of Office Discipline Referrals. Within Classroom Systems, regular acknowledgment of expected behaviors, matching instruction to student ability, and access to additional support were the strongest predictors of sustained implementation. Results are discussed in terms of critical areas for focusing PBIS training to increase the likelihood of sustained implementation.