In preschool settings, the majority of interventions are individualized for children at high risk for challenging behavior. However, a few early childhood sites have begun to conceptualize and implement prevention and intervention initiatives modeled after the principles and key features associated with school-wide positive behavior support. In preschool settings, these efforts are referred to as program-wide positive behavior support (PWPBS). This article presents the findings of a descriptive evaluation in which 62 key stakeholders participated in focus group interviews to assess the social validity of a PWPBS initiative in the 1st year of implementation and to provide recommendations for how to improve the implementation effort. Other data sources included teacher surveys and classroom observations related to PWPBS goals and procedures, conducted intentionally to contextualize the social validity data gathered through the interviews. Results suggest that key stakeholders enthusiastically support the goals of the approach; perspectives about the procedures and outcomes varied considerably. Classroom observation and teacher survey data augment the qualitative data. Implications for model conceptualization and technical assistance efforts are discussed. (Contains 1 figure, 4 tables and 2 notes.)