This article examines what occurred within schools successfully implementing and sustaining Schoolwide Positive Behavior Supports through the lens of leadership capacity. Leadership capacity, a broad-based, skillful participation in leadership, promotes the capabilities of many organizational members to lead. Researchers used quantitative analysis to compare responses of teachers in schools identified as successfully sustaining school improvement (Group 1) with responses of teachers in schools identified as not yet successfully sustaining improvement (Group 2). Results showed a significant difference between the 2 school groups in six characteristics of leadership capacity. The qualitative data revealed that the principals of successful schools demonstrated behaviors that promoted, supported, and encouraged the building of leadership capacity for lasting school improvement. Three themes important to successful schools emerged: (a) empowering communication; (b) purposeful, skillful decision making; and (c) a culture of professional growth. The results showed the importance of understanding change and promoting professional development for educators. (Contains 2 tables and 1 figure.)