In this study, we assessed the feasibility and social validity of an adapted approach to positive behavior interventions and supports (PBIS) implementation in secure juvenile facilities. The authors developed a comprehensive model of facility-wide positive behavior interventions and supports (FW-PBIS) for use in secure juvenile correctional facilities, both detention and long term, as well as state and privately run. FW-PBIS leadership team members that included all major facility roles (education, corrections, mental health, medical, recreation) participated in staff development activities and implemented the advocated approaches over the course of the study. We assessed the fidelity, feasibility, and social validity of FW-PBIS in a repeated-measures evaluation study across 50 secure juvenile facilities. We collected intervention fidelity data using a version of the School-Wide Evaluation Tool modified to reflect the unique features of secure juvenile facilities. We also gathered behavioral incident data from the facilities, but it was not possible to combine these data across sites due to the vast differences in data collection, definitions/classifications, and storage systems from state to state. Results indicated that all participating facilities were able to achieve acceptable FW-PBIS implementation fidelity. Staff rated the intervention as acceptable, feasible, and were willing to implement FW-PBIS practices. Staff members also reported gains in sense of efficacy in their roles. Results are discussed in terms of limitations of the current study, future research, and practice needs.