The behavioral integration and ambidextrous innovation (i.e., balancing and choosing between exploitative innovation and exploratory innovation) of top management team are widely recognized as critical for achieving business success in the corporate management literature. However, behavioral integration and ambidextrous innovation has rarely been examined in the project management literature in general and the realm of megaprojects in particular. To fill this gap, based on the upper echelon theory and ambidextrous organization theory, the theoretical model of "Behavioral Integration-Ambidextrous Innovation-Megaproject Performance" of top management team is constructed. Using quantitative data from 78 top management team members, partial least squares structural equation modeling (PLS-SEM) analysis is conducted, verifying the theoretical hypotheses. The results emphasize that cooperative behavior, information exchange, and joint decision-making have significant positive effects on megaproject performance. Furthermore, the results show exploitative innovation plays an intermediary role between behavioral integration and megaproject performance, while exploratory innovation has no significant mediating effect. Moreover, the findings underscore the megaproject performance relies more on exploitative innovation than exploration innovation. This study not only extends the upper echelon theory and ambidextrous organization theory into megaproject scenarios, but also has some important enlightenment to the megaproject management practices.