This study assessed the Internal Control System as a fraud-prevention mechanism in the Nigerian banking sector. The goal was to determine whether this accomplished the intended result, particularly in famous Nigerian banks. To that goal, the study purposefully collected data from five Nigerian commercial banks. The information was gathered from bank audited and publicized financial statements, and it was examined using the Product Moment Correlation Coefficient and regression analysis. According to the data, the Internal Control System has considerably avoided and reduced fraud in Nigerian banks. That poor corporate governance was to blame for the proper design of the Internal Control System, and that the Internal Control System has resulted in a rise in the corporate performance of Nigerian banks. Based on the findings, it was recommended that the management of each bank create and implement a standard Internal Control System that is strong enough to withstand the wiles of fraud in order to promote operational continuity and to ensure the banks' liquidity or solvency and going concern concept.