A fuel injection control system of an internal combustion engine includes injection setting means, rotational speed change detecting means, and injection control means. The injection setting means calculates the required number of injections and the required injection times with regard to a plurality of fuel injections, based on operating conditions of the engine. The rotational speed change detecting means determines whether the amount of change of the engine speed is equal to or larger than a predetermined value. When it is determined that the amount of change of the engine speed is equal to or larger than the predetermined value, the injection control means controls a fuel injection valve so as to reduce or eliminate differences between the actual injection times and the required injection times. In this manner, even when the engine speed changes rapidly, deteriorations in the driveability and exhaust emissions are prevented.