Despite the burgeoning literature on professionalism in other health professions, psychology lags behind in the level of attention given to this core competency. In this article, we review definitions from other health professions and how they address professionalism. Next, we review how this competency evolved within health service psychology (HSP), and we propose a definition. We offer an approach for assessing professionalism within HSP. Consideration is given to strategies and methods for providing effective education and training in this multifaceted competency. (...) Finally, recommendations are made for creating a culture of professionalism within HSP and honoring psychology’s social contract with multiple publics. (shrink)