Sport psychology has experienced substantial growth in the past decade. Despite many positive developments, however, a nagging question remains. Specifically, what are the boundaries of sport psychology? In this paper, an organizational model is provided as one way of defining sport psychology and related domains of inquiry: exercise psychology, health psychology, and rehabilitation psychology. The process of defining boundaries for sport psychology goes far beyond simple semantics. Failure to reflect and work toward resolution of this issue will continue to restrict the direction and breadth of research, jeopardize appropriate training of graduate students, and maintain definitional ambiguity in the public sector.