This research aims to determine the influence of internal audit, the effectiveness of internal control, and organizational culture on preventing fraud at the Bank Mandiri Madiun City Branch Office. The population in this study were all employees who worked within the Bank Mandiri Madiun City Branch Office, totaling 60 employees consisting of 20 employees from the Bank Mandiri Branch Office Jalan Panglima Sudirman and 40 employees from the Bank Mandiri Branch Office Jalan Pahlawan Madiun City. Sample determination used purposive sampling. with the criteria of employees serving on the Audit Committee, Risk Monitoring Committee, Risk Management, and Integrated Risk Management so that the total sample in this study was 37 respondents. This research is a type of quantitative research with primary data originating from distributing questionnaires. All data collected in this research was analyzed using a multiple linear regression analysis model with the SPSS program. The testing stages in this research include descriptive statistical analysis, data quality testing, classical assumption testing, multiple linear regression analysis, and hypothesis testing. The results of the research show that: (1) Internal audit has a significant effect on fraud prevention at Bank Mandiri Madiun Branch Office ( 2) The effectiveness of internal control has a significant effect on preventing fraud at Bank Mandiri Madiun Branch Office (3) Organizational culture has a significant effect on preventing fraud at Bank Mandiri Madiun Branch Office (4) Internal audit, effectiveness of internal control and overall organizational culture simultaneously has a significant influence on fraud prevention.