Implicit morality theories refer to people’s beliefs about whether individuals’ moral character is fixed or malleable. Drawing on the social cognitive theory of morality, we examine the relationship between employees’ implicit morality theories and their organizational citizenship behaviors toward coworkers (OCBC) and coworker-directed deviance (CDD) through a moral self-regulatory mechanism. A laboratory experiment (Study 1), an online experiment (Study 2), and a multi-wave, multi-source field survey (Study 3) found that the more employees held a fixed belief about morality, the lower (...) their sense of moral control, especially when their moral identity was lower. This perceived lack of moral control, in turn, predicted decreased OCBC, particularly when the workgroup ethical climate was weak. However, this relationship did not hold for CDD. Overall, our research highlights implicit morality theories as a novel antecedent of employees’ workplace behaviors, and identifies the underlying moral self-regulatory process, along with individual and situational boundary conditions. (shrink)