A cooling system of a hybrid vehicle includes a radiator, an openable and closable first shutter, an openable and closable second shutter, and a control device. The radiator is placed forward of an internal combustion engine and a heat generation device configured to generate heat along with operation of the drive motor, and the radiator communicates with the heat generation device and the internal combustion engine such that a coolant circulates through the internal combustion engine and the heat generation device. The first shutter extends from a front end of an undercover so as to cross between the radiator, and the heat generation device and the internal combustion engine. The second shutter extends between a front end part of the undercover and a lower part of the radiator. The control device controls opening and closing of the first shutter and the second shutter.