Behavioral integration (BI), or the extent to which top management team (TMT) members engage in collective interactions, is a critical element for achieving business success in corporate management that has rarely been examined in megaproject studies. The organizational complexities of megaprojects contribute to biases in TMT's behavior. This study presents a team-level analysis of the drivers of BI in megaprojects through the theoretical lens of social capital. Based on a survey conducted with 128 senior managers from 48 megaprojects, the results showed that (1) both the structural and cognitive dimensions of social capital have a significantly positive effect on BI, with the structural dimension being more influential; (2) the relational dimension of social capital showed a partial effect on BI; (3) affective commitment plays a mediating role that bridges social capital and the TMT's BI. These findings shed new light on cultivating interactions among TMT members in governing megaprojects.