A fuel supply control system for an internal combustion engine wherein a basic fuel amount supplied to said engine can be calculated according to the intake air flow rate detected by said intake air flow rate sensor. An air-fuel ratio correction coefficient can be calculated for correcting an amount of fuel to be supplied to the engine so that the detected air-fuel ratio coincides with a target air-fuel ratio. At least one correlation parameter vector which defines a correlation between the air-fuel ratio correction coefficient and the intake air flow rate detected by the intake air flow sensor, can be calculated using a sequential statistical processing algorithm. A learning correction coefficient relating to a change in characteristics of the intake air flow rate sensor can be calculated using the correlation parameter. An amount fuel to be supplied to the engine can be controlled using the basic fuel amount, the air-fuel ratio correction coefficient, and the learning correction coefficient.