The purpose of this qualitative study was to identify critical incidents that helped or hindered the sustainment of Positive Behavior Interventions and Supports (PBIS) in schools with five years or more of implementation in one school division. This study highlighted information related to PBIS because of its comprehensive approach to school discipline. The research sought to answer the following questions: 1. What critical incidents do building-based leadership team members indicate have helped the sustainment of PBIS? 2. What critical incidents do building-based leadership team members indicate have hindered the sustainment of PBIS? Participants of this study included one representative from five different building-based PBIS leadership teams from a school division in the Commonwealth of Virginia. Data were collected and analyzed to determine the building-based PBIS leadership team member's perception of what constituted the sustainment of PBIS, connection between a school's Tiered Fidelity Inventory score and sustainment, key components of implementing PBIS with fidelity, importance of implementing PBIS with fidelity, most challenging sustainable elements of fidelity, and least challenging sustainable elements of PBIS. This research will further contribute to the existing body of literature through a thorough description of critical incidents that have helped or hindered the sustainment of PBIS. Matthews, McIntosh, Frank, and May (2013) stated fidelity is the degree to which a new initiative is delivered as intended in order for PBIS to be sustained. The research identified a need for establishing a stronger understanding of core components of fidelity, establishment of a leadership team, staff buy-in, data driven decisions, and building capacity. Participants also indicated the essentialness of consistency in establishing and utilizing school-wide expectations. Leadership team members emphasized the importance of administrative support from initial stages of implementation through sustainment. In addition, the study found resources to be a vital component to the reward system of PBIS. Participants discussed struggles they endured without proper resources. Ongoing training was also designated as a critical component of sustaining PBIS. Participants similarly indicated the consistent use of data was essential to setting goals and action planning. / Doctor of Education / The purpose of this qualitative study was to identify critical incidents that helped or hindered the sustainment of Positive Behavior Interventions and Supports (PBIS) in schools with five years or more of implementation in one school division. For purposes of this study, critical incidents are those key factors – both positive or negative – that impact the sustainment of PBIS. Educators often times adopt new practices that fail because the root of the concerns were never identified and addressed. PBIS' comprehensive approach to behavior adds value to the school climate, however, there is not much research about sustaining PBIS. The researcher sought to identify these incidents as a means of helping educators sustain PBIS beyond a five-year period. The data from this study could be used to develop guidelines for sustaining PBIS. The researcher interviewed one building-based leadership team member from five different schools to gain an understanding of what constituted sustaining PBIS, key components of fidelity, purpose of the Tiered Fidelity Inventory (TFI) score, and challenges of implementing PBIS with fidelity. This study sought to answer the following research questions: 1. What critical incidents do building-based leadership team members indicate have helped the sustainment of PBIS? 2. What critical incidents do building-based leadership team members indicate have hindered the sustainment of PBIS? Participants of this study included one representative from five different building-based PBIS leadership teams from a school division in the Commonwealth of Virginia. Data were collected and analyzed to determine building-based PBIS leadership team members' perception of what constituted the sustainment of PBIS, connection between a school's TFI score and sustainment, key components of implementing PBIS with fidelity, importance of implementing PBIS with fidelity, most challenging sustainable elements of fidelity, and least challenging sustainable elements of PBIS. The TFI is an assessment tool used to determine the level of fidelity school personnel are applying the core features of PBIS (VTSS, 2018). This research will further contribute to the existing body of literature through a thorough description of critical incidents that have helped or hindered the sustainment of PBIS. Matthews et al. (2013) stated fidelity is the degree to which a new initiative is delivered as intended in order for PBIS to be sustained. This research found a stronger understanding of core components of fidelity needed to be established. Participants also indicated the essentialness of consistency in establishing and utilizing school-wide expectations. Leadership team members emphasized the importance of administrative support from initial stages of implementation through sustainment. In addition, this study found resources to be a vital component to the reward system of PBIS. Participants discussed struggles they endured without proper resources. Continuous training was also designated as critical component of sustaining PBIS. Participants similarly indicated consistent use of data was essential to setting goals and action planning. These identified critical incidents could be used to create guidelines to help educators sustain PBIS beyond a five-year period.