In customer interactions, emotional display rules typically prescribe service providers to suppress negative emotions and display positive ones. This study investigated the causal impact of these emotional display rules on physiological indicators of workers' stress and performance. Additionally, the moderating influence of personality was examined by analyzing the impact of trait anger. In a simulated call center, 82 females were confronted with a complaining customer and instructed to react either authentically and show their true emotions or to "serve with a smile" and hide negative emotions. Increases in diastolic blood pressure and heart rates were higher in the smile condition, while verbal fluency was lower. Trait anger moderated the effects on diastolic blood pressure and observer ratings' of participants' professional competence, suggesting more negative effects for high trait anger individuals. Findings imply that emotional display rules may increase call center employees' strain and that considering employees' personality may be crucial for precluding health and performance impairments among call center workers.