Employees' unethical pro-organizational behavior (UPB) in the workplace, though violating social ethical norms, benefits the organizations. Generally speaking, this behavior is a combination of both self-interest and altruistic motivation. This study, based on the affective event theory (AET), multiple hierarchical regression and confirmatory factor analysis and empirical test using data collected from 6 pharmaceutical enterprises from Beijing and Harbin, constructs a moderated mediation model in which the affective commitment acts as a mediator and positive mood as moderator, testing the internal influential mechanism of the caring ethical climate on UPB. The results of the study demonstrate that the caring ethical climate has significant and positive effects on UPB; the affective commitment partially mediates the relationship between the caring ethical climate and UPB; the positive mood positively moderates the relationship between the affective commitment and the caring ethical climate as well as the relationship between the affective commitment and UPB.