This study was conducted to investigate the determinants affecting the quality of audit services in Vietnam, from the perspective of auditing clients – the Foreign Direct Investment (FDI) clients. Based on the adjustments of SERVQUAL model, the article has discovered five out of six factors that positively affect audit service quality of historical financial statements at FDI enterprises in Vietnam, namely: tangibles, reliability, responsiveness, assurance and non-audit services. Data used in the study was collected from 250 accountants and directors at FDI enterprises in Vietnam. The Exploratory factor analysis (EFA) and Linear regression model were used to identify the factors that affect the quality of audit services. Findings from empirical research are the basis for recommendations for audit firms to enhance the quality of audit services in Vietnam.