While there is a wide body of research to support the effectiveness of schoolwide positive behavior support (PBS), there are significant challenges to facilitating sustainable implementation. The present study begins to address these challenges by exploring PBS implementation in a diverse, regionally isolated elementary school that previously received substantial state-level support for implementation of schoolwide PBS. Follow-up conducted 4 years after the removal of external supports revealed significant persistent challenges with the collection and maintenance of schoolwide data, a decline in implementation at the universal level, and a lack of administrative commitment to schoolwide PBS. The challenges experienced by this school are used to illuminate critical factors for sustained implementation of schoolwide PBS, followed by a discussion of sustainable practices in the areas of administrative leadership, data-based decision making, resource allocation, and technical expertise. Finally, suggestions for future research related to these challenges are offered. (Contains 1 table.)