Organizational citizenship behavior (OCB) refers to a set of voluntary and optional behaviors that are not considered the person’s obligation; however, they are adopted by the person, and they can improve the organizational tasks and roles. This research aims to explain the effect of the dimensions of organizational citizenship behavior (OCB) on customer satisfaction in a case study of Saman Bank branches in Tehran. The results of the research can direct the organizational managers towards success, especially in service organizations. In terms of purpose, the research is an applied one, and in terms of data collection, it is a descriptive survey study. The population includes two groups; the first group consists of the Bank employees in the selected branches of Tehran, and the second group consists of the Bank customers with an infinite number. The research validity was evaluated based on face validity, reliability was evaluated based on Cronbach’s alpha coefficient, normality of data distribution was checked by the Kolmogorov-Smirnov test, and the studied constructs were approved by confirmatory factor analysis and structural equation modeling. According to the results, organizational citizenship behavior has a significant direct and positive effect on customer satisfaction.