Auditing quality is the level of customer satisfaction with the objectivity and reliability of the audit service (Ministry of Finance, 2012). This study explores the relationship between service quality and the loyalty of customers in Vietnamese domestic independent auditing firms. This study was conducted in Hanoi, Vietnam, based on a sample of 250 general accountants and chief accountants who are working for customer firms with transactions at Vietnamese domestic independent auditing firms in Hanoi city. Based on the collected data, we run Cronbach’s alpha, exploratory factor analysis (EFA), Kaiser-Meyer-Olkin (KMO) test, Barlett’s test, and regression using SPSS software. The results show that service quality positively affects the loyalty of customers (LOY), including reliability (REL), responsiveness (RES), assurance (ATT), empathy (EMP), and tangibility (TAN). Moreover, it recognizes the higher weight of customer loyalty in firms. The research determined that service quality can promote customer loyalty. Besides, the services of domestic independent auditing firms have many different characteristics compared to other industries. Therefore, there is a need for more studies on the relationship between service quality and customer loyalty in the audit field. From there, it contributes to perfecting the theoretical framework on customer loyalty and is a useful reference for domestic independent auditing firms, auditors, and audit researchers.