Despite the importance of sustained and continued use of healthcare information systems to reap their benefits of cost reductions and quality improvements, research on continuance use of these systems is limited. In this paper, we study physicians’ continuance to use a pain management clinical decision support system by developing a theoretical model that integrates Delone and McLean IS success model with physicians’ professional identity constructs, an integration that addresses the gap of separating information systems constructs from physicians’ idiosyncrasies constructs in extant literature. We conduct our study through a mixed methods longitudinal design that addresses our research questions. This study enhances our understanding of factors influencing physicians’ continuance behavior and extends current literature on healthcare information systems use.