Drawing on the stressors-emotion model, the present study examines how customer mistreatment behavior (internal stressor) and team performance pressure (external stressor) work together to influence employees’ proactive customer service performance. We propose that customer mistreatment results in employees’ emotional exhaustion, and in turn reduces proactive customer service performance. In addition, team performance pressure interacts with customer mistreatment behavior to influence employees’ emotional exhaustion, such that team performance pressure strengthens the dysfunctional effect of customer mistreatment behavior on employees’ emotional exhaustion. To mitigate this negative effect, we introduce leader positive affective presence as another moderator that attenuates the negative effect of employees’ emotional exhaustion on their proactive customer service performance. Based on time-lagged data collected from 220 employees and 54 branch leaders from a large catering group in China, the results generally supported our hypotheses. The findings advance our knowledge of how internal and external stressors influence employees’ proactive behaviors and provide insights for organizational managers.