Most online social network (OSN) users have exchanged health-related information on OSNs to manage their health, obtain support, and offer assistance to others facing similar medical challenges. Nonetheless, OSN users are concerned about the privacy of their health information. Extant studies on online information privacy have largely resorted to a calculus perspective, focusing on the roles of costs and benefits in information exchange with commercial vendors. Such a perspective, however, fails to capture the nuanced flows of personal health information (PHI) on OSNs, which involves more than two parties. To address this gap and further advance the research on information privacy, this paper embraces the theory of contextual integrity to explore the distinctive contextual idiosyncrasies of PHI flow on OSNs. In particular, we examine how context-specific values and norms affect OSN users’ personal privacy norms and their PHI disclosure intentions. Our theory-driven empirical results suggest that contextual values and normative expectations related to technology control, legislation, and peer users collectively influence OSN users’ personal privacy norms. In addition, perceived personal and altruistic values serve as motivators to promote PHI disclosure intentions, working in tandem with personal privacy norms. The key findings of the study also have important implications for policymakers and OSN providers in the context of OSN-mediated healthcare through 1) advancing our understanding of the complex dynamics of PHI flow on OSNs, and 2) designing effective information privacy measures (i.e., policies, technical features, and programs) to uphold contextual integrity and nurture the development of patient-centered healthcare paradigms.