Professional social networks (PSN) are online environments where practitioners can present themselves, get in contact and socialize with coworkers, share and discuss ideas, or exchange business-related knowledge. Despite the fact that collaboration and information sharing are becoming more relevant for delivering high-quality services, PSN are not yet widely adopted in complex domains such as health care. While most of the literature is still focusing on the exposition of the unbound potential of PSN, this paper seeks to clarify the question of how to capture and manage the professional identity of an industry such that PSN can be purposefully anchored in the working context. Following an Action Design Research approach, we describe practical design propositions and possible tensions along the contextualization of a PSN, which was specifically catered for improving interprofessional and interorganizational collaboration in and between hospitals. We identify several implications for future research. In particular, we explain intended and unintended uses of PSN in hospitals and provide metaphors for explaining possible alternative understandings of domain engineering.