In this study, the relationship between teachers' perceptions of a departmental professional community and teachers' sense of efficacy was examined, along with the degree to which vicarious experience and verbal persuasion might mediate this relationship. The definition of professional community within this study was partially modeled after the work of Louis, Kruse, and Bryk (1995), reflecting teachers' perceptions of the presence of reflective dialogue, deprivatized practice, collaboration, and shared norms within their academic departments. It was expected that teachers who perceived opportunities to talk with one another about student learning (reflective dialogue), observe other teachers during their work in the classroom (deprivatized practice), and collaborate with other teachers would have a higher sense of efficacy than those teachers who did not perceive these features of a departmental professional community. Furthermore, teachers who believed they worked within a department in which colleagues shared norms and values regarding student learning were also expected to experience higher levels of efficacy than those who did not. Finally, it was expected that the relationship between teacher efficacy and professional community would be mediated by vicarious experience and verbal persuasion, two of the four principal sources of information discussed in Bandura's (1977) self-efficacy theory. A total of 229 teachers from nine high schools in a middle-class school district participated in the study. Results from hierarchical regression analyses indicate that: perception of a departmental professional community was a significant and positive predictor of teachers' overall efficacy and efficacy for classroom management, instructional practices, and student engagement; of the four community features, teachers' perception of shared norms and values within the department was the strongest and most consistent predictor of efficacy; deprivatized practice was a significant and positive predictor of teachers' efficacy for instructional practices; and the mediation model was not significant. Furthermore, teachers' view of ability as incremental or fixed was a consistent negative predictor of efficacy, while teachers' years of experience was a significant positive predictor. Teachers' perceptions of student performance emerged as the strongest predictor of teachers' efficacy beliefs. Implications of findings and directions for future research are discussed.