The successful implementation of school-wide positive behavior support (SWPBS) relies greatly on staff's commitment and buy-in, as these factors directly impact the level of their involvement and engagement. As such, it is crucial to develop and use psychometrically sound tools to measure staff's supportive beliefs regarding SWPBS. In this study, we conducted a series of psychometric analyses of a 30-item adoption from the Beliefs About Behavior Survey (BABS) to assess staff's perceptions of key SWPBS components. The research involved 767 school staff members in two mid-mountain U.S. states. An exploratory factor analysis (EFA) performed on data from one state (N = 376) resulted in an 18-item survey addressing four distinct factors: Positive System Practice, Proactive Prevention, Use of Punishment, and Equity and Fairness. The results of reliability estimates supported the survey's internal consistency. The four factors collectively accounted for 57% of the variance among the items, indicating adequate psychometric properties. A subsequent confirmatory factor analysis (CFA) using data from the second state (N = 391) demonstrated an adequate data-model fit for the four-factor structure. This brief and cost-efficient survey instrument can be used to assess staff support or resistance to SWPBS, enabling data-driven decisions for planning professional development and system support. The study's limitations and potential future research directions are also discussed.