This paper aims to analyze and compare the efficiency level of Bank Syariah Indonesia (BSI) before and after the merger. BSI began to merge in 2021 with three banks: Bank Syariah Mandiri (BSM), BNI Syariah, and BRI Syariah. The results showed that the ratio of Operating Expenses to Operating Income (BOPO) improved after the merger. Meanwhile, other ratios, such as the Financing to Deposit Ratio (FDR), did not change after the merger. Different research results show that mergers have an excellent impact on banks' performance and health levels. The merger of 3 Islamic banks is the right decision.