An engine room cooling system may include an encapsulation covering an intake manifold and an exhaust manifold of an engine of a vehicle, a main duct guiding traveling wind flowing into the vehicle to a side of the encapsulation, an encapsulation intake duct branched from the main duct and formed toward the intake manifold within the encapsulation, an encapsulation exhaust duct branched from the main duct and formed toward the exhaust manifold within the encapsulation, and an intake duct valve disposed adjacent to the encapsulation intake duct and controlling air flow from the main duct to the encapsulation intake duct or to the encapsulation exhaust duct.