This study examined customer service quality and its effect on customer satisfaction in commercial bank of Ethiopia at Ambo branch. The study was conducted at one branch. The five service quality dimensions were used to measure the service quality of the bank. The researcher collected data through questionnaire. The respondents were selected through simple random sampling method and the data was analyzed using statistical tools such as mean, standard deviation, correlation and multiple regressions. The findings of this study indicate that the four service quality dimensions (tangibility, empathy, assurance and reliability) have positive and significant effect on customer satisfaction. However, responsiveness has a negative and insignificant effect on customer satisfaction. Providing superior service quality is very crucial for the success and growth of the bank. That means, if the bank provide superior service quality to customers, the customers will be satisfied, if they are satisfied with the service of the bank, they will be loyal customers of the bank. Therefore, the bank should provide superior quality service to customers in order to achieve its goals.