In a fuel level control system for an internal combustion engine, more than one filter having different characteristics is applied to correct the fuel level value according to the condition of the vehicle, providing precise fuel level measurement. The fuel level control system for the engine includes a fuel level correction section in which fuel level detection is prevented until a first set time has elapsed from activation of an ignition switch. The fuel level is detected by the fuel level detector after the first set time has elapsed and the detected fuel level value is corrected with a weak filter of high followability. After a second set time has elapsed the detected fuel level value is corrected with a strong filter of low followability. The strong filter minimizes the effect of disturbances on the fuel level value.