This article examines ways in which entities external to schools, in this case for-profit educational management organizations (EMOs), can influence development of school professional community. Drawing on case studies of six charter schools operated by three EMOs, we examine the five elements of professional community described by Kruse, Louis, and Bryk; supports and barriers to development of professional community; and the role of EMOs in influencing supports and barriers. We found that in these cases, EMO staff influenced professional community in important ways through the design of their programs (including structures they set up for use of time and staffing) and their informal relationships with schools (including their roles as "cheerleaders," constructive critics, flexible keepers of the model, and reliable managers). The findings of this exploratory study provide a basis for future research on how external entities such as EMOs can influence professional community.