Purpose – Project-based supply networks are an emerging form of organizing used to meet a buying organization’s operational and innovation goals. Knowledge sharing among suppliers in the network plays a key role in successful project delivery but is challenging to achieve in practice. We draw on self-determination theory (SDT) to examine the interactive effect of incentive provisions (penalties and bonuses) and network governance (lead or shared) on knowledge sharing motivation by individual boundary-spanners within project-based supply networks. Design/methodology/approach – A scenario-based behavioral experiment of 217 professionals within the UK using the online platform, Prolific, was conducted. A Hayes Macro PROCESS model was used to analyze the data. We pilot-tested the scenario with project management experts, senior managers, and directors. Findings – Our findings highlighted that the effectiveness of incentive provisions on knowledge sharing may be dependent on the mode of network governance. Where suppliers have shared responsibility for managing the network (shared governance), bonuses were more effective than penalties in motivating knowledge sharing through support of boundary-spanners’ autonomy needs. However, where the buying organization has transferred responsibility for managing the network to an external third-party organization (lead governance), we found no significant difference between the effectiveness of penalty versus bonus provisions in motivating knowledge sharing. Originality – Prior research in operations and supply chain management (OSCM) has shown the positive effect of incentive provisions on knowledge sharing motivation, but largely overlooked the effectiveness of such incentives when nested within broader governance mechanisms used in projects and their networks. Moreover, while scholars have started to highlight the importance of governance mechanisms in knowledge sharing at the dyadic level, we know very little about the impact of network governance.