Financial liberalization has led to intense competitive pressures and private banks dealing in retail banking are consequently directing their strategies towards increasing service quality level which fosters customer satisfaction and loyalty through improved service quality. This article examines the influence of perceived service quality on customer satisfaction. In this paper, we have used SERVQUAL as a technique to measure service quality and identify gaps in a BASIC Bank. The results of this study showed that there are service quality gaps between customers’ expectations and their perceptions in six dimensions. In this issue paying attention to the effective factors on customers’ expectations and its relationship with services quality is one of the important issues of the evaluation of services quality. For this purpose, the recent research was performed based on gap analysis model with the purpose of investigating the quality of banking services on the level of BASIC Bank. It was concluded after determining the desirable services from the standpoints of the customers (investigating customers’ expectations) and its effective factors and also the examination of the current status of services quality (customers’ understandings) that BASIC Bank responses to customers’ expectations in all of the branches under investigation and the understood services quality has been always more than services quality expected by the customers.