The purpose of this research is to investigate the impact of employees' destructive behavior on customers' Deviant behavior. This research is applied in terms of purpose and descriptive-survey in terms of nature of the method. The statistical population of the research includes the customers of National Bank branches in Ilam, according to Morgan's table, 384 people were selected for the research sample. The data collection tool in this research is a standard questionnaire whose validity has been confirmed by expert professors and its reliability has been confirmed using Cronbach's alpha coefficient. Lisrel software was used for data analysis. The results showed that the destructive behavior of employees has a positive and significant effect on the Deviant behavior of customers in the branches of National Bank of Ilam. Also, the dimensions of employees' destructive behavior are: violation of laws, corruption of employees, lying to customers, retaliatory Behaviors and aggression at work also have a positive and significant effect on customers' Deviant attitudes in branches of National Bank of Ilam.