Increasing uncertainty in the business world requires organizations to establish temporary, IT-enabled interorganizational information exchanges on short notice. Information sharing among disaster relief organizations represents an extreme case of these ad hoc interorganizational information exchanges, and therefore provides a good reference point for analyzing firms' strategic competitive and cooperative considerations (co-opetition). While ad hoc IT-enabled interorganizational information sharing is particularly crucial in facilitating efficient disaster response, little research has outlined the main barriers and benefits of participation in these ad hoc information relationships, with the existing literature often overlooking the competitive aspects. We demonstrate that the ad hoc humanitarian context of natural disasters provides additional insights to existing understandings of information sharing costs and benefits under co-opetition. An elaborated game-theoretic model is developed that provides a theoretical foundation for empirical and modeling research on IT-enabled interorganizational information sharing, under co-opetition in disaster relief, as well as in other business contexts.