A heat pump system for a vehicle includes an integrated control valve, an external condenser connected to the integrated control valve through first and second connection lines, an expansion valve connected to the integrated control valve through a third connection line, an evaporator connected to the expansion valve, an accumulator connected to the evaporator, a compressor connected to the accumulator, an internal condenser connected to the compressor and connected to the integrated control valve through a fourth connection line, a first chiller disposed on a fifth connection line connecting the integrated control valve and the accumulator, a sixth connection line connecting the fifth connection line and the integrated control valve between the first chiller and the accumulator, and a second chiller provided on a seventh connection line connecting a refrigerant line and the integrated control valve between the evaporator and the accumulator.