The focus of this research is on assessing the quality of services of Tehran’s Saman bank and the available gap between customer’s expectation and perception. Also the relationship between customer’s satisfaction and each dimension of service quality (ie: reliability, tangibility, responsiveness, assurance and empathy) and ranking them accordingly, is investigated. The statistical population of this research is consisted of Tehran’s Saman bank customers. The research methods of this study are descriptive-survey as well as correlation. The statistical approaches of this study are correlation, t-student as well as Friedman tests. The results from a sample of 276, shows the service quality dimensions affect customers & apos; perception based on SERQUAL. In addition, there are significant relationship between customers & apos; perception and their satisfaction of the offered services. However, there are negative gaps between customers & apos; perception and their level of expectation.