Business-to-business (B2B) data sharing promises to add significant value by unleashing innovation potential in organizations. But companies are reluctant to share data. They have security and privacy concerns, fearing opportunistic behavior against them, thus limiting the innovation that could ensue with data sharing. This paper addresses this challenge and investigates how different types of opportunism influence senior managers’ willingness to engage in B2B data sharing. Analyzing 484 data-sharing decisions from 121 Thai managers across varied scenarios reveals that endogenous opportunism promotes data sharing, whereas active opportunistic behavior deters it. Furthermore, the impact of active opportunistic behavior is stronger than that of endogenous opportunism. Interestingly, endogenous opportunism mitigates the negative effects of active opportunistic behavior, demonstrating their intricate interplay. We derive implications from these results.