Customer incivility (CI) is a pervasive problem in service encounters and involves negative consequences for employees and organizational performance. While prior research has focused on the detrimental effects of CI, there is a limited understanding of its antecedents, especially from the customer perspective. To address this gap, this research examined the customer’s cognitive processes underlying CI. Drawing on cognitive appraisal theory, this research hypothesized that customer anger mediates the relationships between negative service experiences and CI and that confirmation bias, overconfidence, and social influence moderate the relationships. Using data from consumer surveys (Study 1) and TripAdvisor reviews (Study 2), findings show that conflict with employees is a key driver of CI, mediated by anger. Additionally, Study 1 found that confirmation bias and overconfidence moderate the effect of conflict on anger. Moreover, Study 2 showed that social-influence bias moderates the relationship between conflict and anger. These results have theoretical and practical implications for managing CI.