Drawing on the self-enhancement theory, from the perspective of self-enhancement motivation and Machiavellianism, the research tries to explore the relationship between leadership ostracism and employee unethical pro-organizational behavior, explaining whether, how and when leadership ostracism might promote employee unethical pro-organizational behavior. Participants of this study were 451 employees from Chinese companies. The results of this research are as follows. Leadership ostracism has a significant positive impact on employee unethical pro-organizational behavior. Self-enhancement motivation plays a mediating role between leadership ostracism and employee unethical pro-organizational behavior. Machiavellianism moderates the relationship between employee self-enhancement motivation and unethical pro-organizational behavior, such that the effect of self-enhancement motivation on unethical pro-organizational behavior is stronger when Machiavellianism is high rather than low. Moreover, employee Machiavellianism moderates the indirect effect of leadership ostracism on unethical pro-organizational behavior via self-enhancement motivation, such that the indirect effect is stronger when Machiavellianism is high rather than low.