An object is to provide a technology that enables starting of fuel injection under a condition that allows injected fuel to ignite and burn at the time of start-up of an internal combustion engine. To achieve the object, a start-up control system for an internal combustion engine according to the invention estimates, at the time of start-up of the internal combustion engine, the amount of rotation of a crankshaft in a period since the start of cranking until a crank position sensor outputs an effective pulse signal and determines, based on the stopping position of the crankshaft specified by the value thus estimated, whether or not fuel is to be injected at the first fuel injection time.