The purpose of this study was to examine the effect of relationship marketing on customers’ frequent use of services provided by an Iranian bank named Eghtesad Novin (EN). The present study was a correlational-applied study. The population of this study was all customers who had more than two years of collaboration with the EN Bank and were living in Tehran. Therefore, those branches located in diverse districts of Tehran were selected from all branches across the country. Since each branch was associated with one of quadripartite districts, five branches were selected randomly from each district. Multi-phase cluster random sampling was carried out in these districts. To obtain a sample size, formula of ratio estimation with a relative error of 0.05 and a maximum variance value of 0.50 were used so that the total size of sample was determined as 400 approximately. This study utilized the descriptive survey method. For this purpose, researcher-made questionnaires were used. In order to determine the reliability of the above-mentioned questionnaires, Cronbach & apos; s alpha coefficient was used and it was determined as 0.813, which confirmed the questionnaires. In addition, the validity of these questionnaires was reviewed and confirmed using expert opinions and viewpoints of professionals working in the banking sector as well as respectful professors. Inferential statistics as well as SPSS and LISREL software were used in order to design the research model. To this end, the effect of the foundation of relationship marketing including commitment, trust, communication and conflict-handling on customer loyalty, the importance of these factors from the perspective of the customers and the bank & apos; s success in creating any of the variables was examined and the data was analyzed using multiple regression method. The results showed that, except commitment, other foundations of relationship marketing had significant and positive effects in this bank.