A thermal management system for a vehicle and method for controlling a water-heating type PTC heater thereof by controlling a PTC heater that uses water for heating, in which a heat source for heating is secured by operating the water-heating type PTC heater and thereby additionally heating a coolant, while charging a battery, in a thermal management system for a vehicle, during a heating mode, in which: refrigerant circulates through a second heat exchanger, a waste heat recovery chiller, a compressor and an indoor heat exchanger; and the coolant passes through a water-cooling type battery module, the water-heating type PTC heater, a battery chiller, electric parts and the waste heat recovery chiller.