In Indonesia there are already many Islamic banks, but there are still many Sharia banks that have not fully implemented the Sharia system in carrying out their operations or there are still Sharia banks that violate Sharia principles. Therefore this study aims to find out how the supervision carried out by the Sharia Supervisory Board and the Financial Services Authority in supervising Islamic Financial Institutions. This study used qualitative research methods. By using data collection techniques namely Purpose sampling. Data collection was carried out through interviews with resource persons from the Sharia Supervisory Board and BPRS to Build Citizens' Degrees and the Yogyakarta Financial Services Authority. The results of the study show that the synergy between the BPRS sharia supervisory board BDW and the Yogyakarta financial services authority in carrying out supervision is very important to run banking operations based on sharia principles and realize a financial system that grows stably and sustainably. This was demonstrated by supervision carried out by the sharia supervisory board in supervising the operations of Islamic banking so as not to get out of sharia principles and financial service authorities that oversee all activities running within the financial sector, including sharia banking. The stronger the synergy between the shariah supervisory board and the sharia financial services authority in conducting supervision, the greater the opportunity to minimize violations of sharia principles.