Although customer mistreatment has harmful consequences for employees and the organization, the boundary conditions of customer mistreatment have been largely neglected. This study conceptualizes Customer Mistreatment (CM) as a signaling failure regarding employees’ pursuit of tasks and social goals at work and aims to examine the impact of CM on employees’ extra-role performance through the mediating role of rumination. In addition, the moderating role of Hostile Attribution Bias (HAB) in the link between CM - rumination was also investigated. The Partial Least Squares Structural Equation Modelling (PLS-SEM) was used for data analysis, including measurement and structural assessment. Based on the data collected from 200 frontline staff working at Tan Son Nhat international airport, the findings revealed that CM indirectly affects employees’ extra-role performance via rumination. Besides, although HAB did not moderate the thee CM - rumination relationship, it did impact employees’ rumination. Limitations, recommendation for future research, and implications are discussed.