The purpose of this study was to identify factors associated with sustainability of school-based interventions and the relative contributions of those factors to predicting sustained implementation of Schoolwide Positive Behavior Support (SWPBS). Participants were respondents from 217 schools across 14 U.S. states. Sustainability factors were assessed through a research-validated measure, the School-wide Universal Behavior Support Sustainability Index: School Teams (SUBSIST; McIntosh, Doolittle, Vincent, Horner, & Ervin, 2009), and sustained implementation was measured by meeting implementation criteria on research-validated measures of SWPBS fidelity of implementation. Factor analyses revealed 2 school-level factors, School Priority and Team Use of Data, and 2 district-level factors, District Priority and Capacity Building. All factors were significantly related to sustained implementation, but only Team Use of Data and Capacity Building were significant independent predictors. Results are discussed in terms of future sustainability research and implications for enhancing the sustainability of school-based interventions.