In recent years, the quality of auditing human resources in domestic auditing firms in Hanoi has certain limitations in which professional skills of auditors have not been given adequate attention. The number of customers at local auditing firms is forecast to increase gradually. Therefore, the quantity and quality of auditors need to be improved to meet requirements of the workload. Data for this research were collected through surveying 120 customers of domestic auditing firms in Hanoi on the 5-point Likert scale. Based on the collected data, we employ both qualitative and quantitative methodology along with some tools such as descriptive statistics, Cronbach's Alpha, T-test and ANOVA to analysis, evaluate and measure the professional skills of auditors in local auditing firms in Hanoi. The results show that the professional skills of auditors in auditing firms include 17 attributes. The majority of respondents show appreciation for the professionalism and professional competence of auditors, while, they think that critical thinking skills and creative thinking skills are still limited and need to be improved. These findings, not only help auditors to improve themselves, but also provide solutions for managers of domestic auditing firms in Hanoi to enhance quality of audited human resources.