The frontline service employee-customer relationship is crucial for organizational success. Given the inherent unpredictability of service encounters, employees must internalize organizational standards through strong moral and motivational dispositions, reinforced by effective leadership. We demonstrate that deficiencies in these areas increase deviant service behaviors that harm customer relationships and organizational goals. Specifically, we investigate Service Sabotage (actions that undermine customer relationships) and Deviant Service Adaptation (DSA; excessive discretionary action that undermines business objectives). Our findings reveal that moral identity internalization mitigates Service Sabotage, while both moral identity internalization and self-determination theory (SDT) mitigate DSA. Ethical leadership strengthens the impact of moral identity internalization on Service Sabotage but has mixed effects on DSA. We also explore the mediating mechanisms of SDT within the service encounter.