Recently, competition has shifted from the firm to the network level. Following this path, a growing stream in IT value research has emerged, aiming to understand how multiple firms create value through joint IT resources and capabilities. Despite the efforts made thus far, there are inconsistencies regarding construct definitions and divergent empirical findings. In this paper, we synthesize and integrate the body of knowledge on IT-based value co-creation. Drawing on the relational view, we first synthesize the existing empirical findings. The results of a meta-analysis of 72 studies encompassing 33,732 observations underline the importance of four sources of IT value: IT-based inter-organizational assets, IT-based knowledge sharing, IT-based complementary capabilities, and IT-based governance. A further moderator meta-analysis integrates divergent empirical findings in the literature. We find that objective measures dampen the relationship between inter-organizational IT and business value, while process-level measures and IT capabilities strengthen it. Moreover, we find evidence for higher value impacts in developing countries and an influence of inter-organizational relationship types. This study contributes by clarifying the IT-business value relationship and offers insights into sources of inconsistencies in IT-based value co-creation studies. By doing so, this paper lays a foundation for future research and theory development.