Nowadays, the competition between companies are tight, in order to survive in this competitive world, companies need to not only improve the quality of products, but also improve the quality of service. Quality of service is one of the factors that affect customer satisfaction. Companies have also been upgrading their quality of service to give an unfamiliar good feeling to the customers and to achieve their goals through 4P, which includes product, place, price and promotion. This study aims to know the effect of the quality of service on customer satisfaction at Bank CIMB Niaga - Asia Medan branch. This research was conducted on 50 respondents of Bank CIMB Niaga. The sampling type used in this study is non-probability sampling and census method. The data collection method is through online questionnaire which is filled by Bank CIMB Niaga customers at Asia Medan branch. The result of this research shows that the coefficient of correlation was 40.6%, it shows the relation of quality of service on customer satisfaction at Bank CIMB Niaga and 16.5% of customer satisfaction can be explained by quality of service while the remaining 83.5% can be explained by other factors. The results of this research can be used by Bank CIMB Niaga at Asia Medan branch to improve their quality of service to gain customer satisfaction. Recommendation for future researchers are competitors should be taken into consideration, larger sample size and to use other factors that may also influence customer satisfaction.