Sharing knowledge among multiple organizations is key to addressing adaptation challenges and unforeseen issues involved in the delivery of complex projects. While much research has focused on governance and institutional factors within these projects, less attention has been paid to individual boundary spanners, who act as gatekeepers for the transfer of knowledge to other organizations. We draw on self-determination theory to examine how the mode of governance (shared versus lead) and motivational climate (mastery and performance) affects psychological needs satisfaction, and ultimately, boundary spanners’ knowledge sharing motivation. Results from a behavioral experiment of 256 managers shows that shared versus lead modes of governance enhance knowledge sharing through psychological needs satisfaction. Moreover, while mastery climate facilitates the needs satisfaction and consequently, boundary spanners’ knowledge sharing motivation, the results do not show a significant effect of performance climate on knowledge sharing.