Audit fees and audit quality have received the attention of stakeholders, clients, audit firms, and third parties. Each subject has its own opinion on determining influencing factors and their relationship. This study aims to investigate the determining factors of audit fees and audit quality in Vietnam. Using random data collection, a questionnaire was created on Google forms and sent to auditors from the 4th quarter of 2020 to the end of the 1st quarter of 2021. 267 valid auditors’ responses in 28 audit firms were used for data analysis. Exploratory factor analysis (EFA) was used to determine relationships between observed variables and factors. The measurement model and recommended hypotheses were confirmed by structural equation modeling (SEM) using SPSS 26 and AMOS 26. The study results show that contract types and audit complexity, audit firms’ reputation, size, and risk significantly impact audit fees and audit quality. In addition, the specialization of the audit firms does not have a positive effect on audit quality but on audit fees. The audit tenure has no statistical impact on audit fees and audit quality. Notably, audit fees statistically affected audit quality. Several implications can be applied, such as increasing the firm size, performing the procedures in response to audit risk, separating audit contract types, and determining the complexity of audit projects and specialties.