According to significant challenges of the banks, there is a greater need to assess the existing banking system and implement corrective actions. In this paper, the financial soundness of 11 Iranian private banks is evaluated by using the CAMELS indicators (Capital adequacy, Asset quality, Management, Earning, Liquidity, and Sensitivity to market risk). The weights of indicators are determined using the Best-Worst Method (BWM). Data Envelopment Analysis (DEA) is consequently used to calculate the efficiency score of the Decision-Making Units (DMUs). Principal Component Analysis (PCA) is used to validate the DEA results. Also, several sensitivity analyses are conducted on private banks. The intuitive results of sensitivity analysis prove accurate as demonstrated by statistical tests. The results of sensitivity analysis and statistical tests demonstrate that Iranian private banks have the best performance in terms of the indicators of Management and Capital adequacy, and the poorest performance in terms of Asset quality. Also, using the Strengths-Weaknesses-Opportunities-Threats (SWOT) matrix, the authors present appropriate strategies for improving the performance of the banking system. To the best of our knowledge, the present study for the first time aims to assess and improve financial soundness of private banks by using a combination of qualitative and quantitative methods.