The development of Islamic cooperatives or Baitul Maal Wat Tamwil (BMT) in Indonesia has led it to provide good service quality to increase the satisfaction of its member and to compete with other institutions. Therefore, this study aimed to prove the relationship between the quality of service and member satisfaction in BMT Maslahah Sedati branch office. This study used a quantitative method with a simple correlation analysis and analyzed using IBM SPSS 25 Version program. The population of this study was all of BMT member with 93 samples of BMT Maslahah Sedati branch office members. The result of this study indicated a relationship between the quality of service and the member satisfaction of the BMT Maslahah Sedati branch office. The correlation coefficient of this study was 0.376 that included a weak category. The relationship between the service quality and member satisfaction showed a weak result because it provided a lack of service and caused the member feeling dissatisfied. The determination coefficient on the quality variable of the service could explain the member satisfaction variable by 30%, and the rest are not tested in this research.