This study investigates whether, why, and when perceived psychological contract breach (PCB) evokes employee destructive voice. Drawing from relative deprivation theory, we develop a moderated mediation model in which personal relative deprivation is theorized as a unique mechanism contributing to why employees who experience PCB are more likely to express destructive voice. Additionally, leader emotional support is proposed to be a relevant boundary condition. Specifically, we propose that the positive relationship between PCB and personal relative deprivation is weakened when leader emotional support is high. Time-lagged supervisor–subordinate matched data was collected to test the model. The results support the hypothesized relationships; that is, personal relative deprivation mediates the relationship between PCB and destructive voice, and this relationship is stronger when leader emotional support is higher rather than lower. Thus, compared with the research using social exchange theory and affective events theory, our investigation suggests a new perspective to understand the negative consequences of PCB.