AbstractCompared with the performance dilemma, how to deliver a megaproject following the principle of sustainability is a more intractable problem. For the sustainable delivery of megaprojects (SDM), contracts and megaproject citizenship behavior (MCB) are two possible governance methods, but their effectiveness and the interaction mechanism have not been given sufficient empirical and theoretical attention. This study proposes a governance framework based on team altruism theory and social exchange theory to explore the respective and interactive governance effects of contracts and MCB on SDM. A partial least-squares structural equation modeling (PLS-SEM) was used to test the hypothesis based on data collected from 197 respondents. The empirical results demonstrate that both MCB and contracts have different degrees of positive impact on SDM. Regarding the moderating effect of contract functions, contractual obligations significantly moderated the relationship between self-concerned MCB and SDM. However, the moderating effect of contractual obligations on the relationship between society-concerned MCB and SDM is nonsignificant. Besides, the moderating effect of contractual supervision is unexpected. Contractual supervision positively moderated the relationship between self-concerned MCB and SDM, but negatively moderated the relationship between society-concerned MCB and SDM. These findings may assist owners and supervisors of megaprojects make informed decisions in effectively guiding the behavior of participants to improve the sustainable delivery performance of megaprojects.