Purpose: Global economic development has increasingly widened banking operations worldwide. The banking industry in Vietnam has shown great development to serve its booming economy. The purpose of this paper is to provide an assessment of business performance in Vietnamese banks from early 2019 until the earlier 6 months of 2020 by means of a Super Slacks-Based-Measure (SBM) model using the Data Envelopment Analysis (DEA) method. Methodology: Three of input variables are identified including total assets, operating expenses, capital and funds; and, two output variables are determined including net interest income, and profit after tax. Data related to twelve Vietnamese banks was chosen in accordance with the given criteria to measure banking efficiency based on the principles shown in the DEA method. Findings: Analysis results identified relative periods of efficiency, relative periods of inefficiency, and the banks’ rankings throughout each period. Based on the principle of slacks of the super-SBM model, a feasible solution was recommended to deal with inefficient periods in particular. Value: The final empirical result exhibited an overall picture of the operational process of Vietnamese bank industry before and within the COVID-19 pandemic.