<p>A common assumption in moral research is that moral identity is inherently positive, often overlooking potential negative outcomes. This study examined the possible negative implications of moral identity from the dual interaction perspective of employees and leaders, focusing on its internal mechanisms and boundary conditions. Data were collected from 548 leader-employee dyads across 85 teams in China. Results from cross-level polynomial regression indicated that leader-employee congruence in moral identity leads to a high level of leader-member exchange (LMX), which subsequently increases the likelihood of employees engaging in unethical pro-supervisor behavior. Furthermore, the positive indirect effect of moral identity congruence on unethical pro-supervisor behavior (through LMX) is stronger when leader power distance is high compared to when it is low. This study underscores the importance of considering both employee and leader moral characteristics in understanding unethical pro-supervisor behavior. This research significantly expands the field of unethical pro-supervisor behavior and enriches our understanding of the dark side of moral identity.</p>