The employees of professional service firms regularly engage in various knowledge-related activities, including the seeking and sharing of knowledge with other people; we refer to this process as interpersonal knowledge exchange (IKE). Two prominent drivers of IKE in China are the socio-cultural concept of guanxi and social media. We conduct an interpretive investigation into IKE, collecting qualitative data from employees in three Chinese organizations. We explore how guanxi lubricates the social media-based communication practices that are central to IKE in China. We report and generalise our findings into theoretical propositions, discuss the practical implications, and identify opportunities for future research.