Abstract: To ensure the success of R&D cooperation, it is vital to reduce opportunistic behaviors within it. This study investigates the relationships between control mechanisms and opportunistic behaviors in R&D cooperation. It finds that both relationships of contract control and trust control to opportunistic behaviors are negative. Moreover, the relationship between contract control and opportunistic behaviors is positively moderated by technologic difference and managerial difference between partners; but that of trust control to opportunistic behaviors is negatively moderated by both types of differences. The findings identify key inhibiting factors for opportunistic behaviors in R&D cooperation and advance our understanding on the implications of control mechanisms. Moreover, the findings can guide firms design control mechanisms to reduce opportunistic behaviors and ensure the success of R&D cooperation.