A heat pump system for a vehicle may include a battery cooling line connected to a battery module and allowing a coolant to flow therein, a chiller connected to the battery cooling line through a first connection line and connected to a refrigerant line of an air conditioner device in which a refrigerant moves through a second connection line to selectively heat-exchange a refrigerant and a coolant introduced to the inside thereof to adjust a temperature of the coolant, an electric/electronic component cooling device electric/electronic component cooling device including a radiator and a first water pump connected through a cooling line to circulate a coolant to cool a motor and an electric/electronic component, and selectively connectable to the battery cooling line and the first connection line through a first valve, and an electronic expansion valve mounted at the second connection line between the refrigerant line and the chiller.