Asset quality is one of the most critical areas in determining the overall condition of the bank. The primary factor affecting overall asset quality is the quality of loan portfolio and the credit administration program. The operational performance of the banks has been analyzed using the financial ratios of the select public sector banks in the pre and post-merger periods. Mergers and Acquisitions as a phenomenon are implemented to strengthen the banking system, embrace globalization, improve healthy competition, exploit economies of scale, adopt advanced technologies, raise efficiency and improve profitability. The main objective of this study to investigates the impact of asset quality on operational performance of public sector banks in the pre and post-merger periods. The study period covers five years pre and post-merger of banks. The year of merger as a base year and hence, it is excluded from the evaluation in order to have consistency in evaluation of pre and post-merger performance of acquirer banks. The year of merger differs in all merger deals. For the purpose of the study, the census method has been adopted to select public sector banks namely the State Bank of India, Indian Overseas Bank, Bank of Baroda, Punjab National Bank, IDBI Bank and Oriental Bank of Commerce. The latest mergers have been taken for sample size of the study i.e. after the year 2000 has been considered. The data analysis is done using ratio analysis, descriptive statistics like mean, standard deviation, coefficient of variation, compound annual growth rate, paired t-test and multiple regression.