This study aims to identify whether banks’ performance post mergers and acquisitions have brought profitability efficiency or not. The data is collected from financial statements of 8 commercial banks in Vietnam, including SCB, PVcombank, HDBank, Sacombank, MSB, BIDV, SHB, and Vietinbank. This study is utilized the DEA approach to estimate and compare the banks’ scores before and after mergers and acquisitions. The results show that mergers and acquisitions almost cannot lead to improved efficiency for acquiring banks, especially in terms of profitability efficiency. This requires Government, the State bank of Vietnam, policymakers as well as commercial banks themselves not only concentrate on mergers and acquisitions but also pay attention to solve difficulty post-restructuring such as non-performing loans, liquidity, and interest risk, capital adequacy ratio, technology, and even personnel issue.