Danish transplant coordinators handle all data and logistics involved with the removal and transfer of organs from the body of an organ donor into several recipients in other Scandinavian hospitals. This entails a wide range of data work, not only in relation to sudden organ donation cases, but also to documenting transplantations, providing feedback on donation outcomes, and facilitating the data needed by surgeons or other health professionals. This article investigates the data practices of organ transplant coordinators through the lens of diplomacy. Based on participant observation and interviews among Danish transplant coordinators, I focus on the cross-disciplinary relations and negotiations characterizing organ exchanges and show how datafication in itself is not enough to ensure smooth transplantation processes. Organ transplantation depends on the diplomatic social skills of the coordinator and the personal relationships between coordinators, surgeons and ICU staff. By bringing into focus the power of diplomacy, I conceptualize these structurally invisible efforts enabling organ donation and its associated data practices. Diplomacy enables us to recognize and understand the relational efforts and aspects of datafication, and the tremendous amount of work and social skill that go into producing and exchanging data in contemporary healthcare