Functional communication training (FCT; Carr & Durand, 1985) is a common function-based treatment in which an alternative form of communication is taught to reduce problem behavior. FCT has been shown to result in substantial reductions of a variety of topographically and functionally different types of problem behavior in children and adults (efficacy). The extent to which these reductions maintain in relevant contexts and result in meaningful changes in the lives of those impacted (effectiveness) is the focus of this paper. This review evaluates the degree to which FCT has been established as an evidence-based practice in psychology (EBPP) according to the definition set out by the American Psychological Association's 2005 Presidential Task Force on Evidence-Based Practice. Our review finds overwhelming evidence in support of FCT as an efficacious treatment but highlights significant limitations in support of its effectiveness. In order to also be recognized as an EBPP, future research on FCT will need to focus more closely on issues related to home, school, and community application, feasibility, consumer satisfaction, and more general and global changes for the individual.