A thermal management system for a vehicle, the system comprising: a cooling apparatus including a radiator, a first water pump, a first valve, and a reservoir tank which are connected through a coolant line, to circulate a coolant in the coolant line to cool at least one electrical component mounted in the coolant line; a battery cooling apparatus including a battery coolant line connected to the reservoir tank through a second valve, and a second water pump and a battery module which are connected through the battery coolant line to circulate the coolant in the battery module; a chiller mounted in a branch line which is connected to the battery coolant line through the second valve and connected to a refrigerant line of an air conditioner through a refrigerant connection line, to adjust a temperature of the coolant by performing heat exchange between a coolant which is selectively supplied to the branch line and a refrigerant which is selectively supplied from the air conditioner, wherein the air conditioner includes a heating, ventilation, and air conditioning (HVAC) module; and a heating circuit including a heater which is connected to the coolant line and the branch line through first and second connection lines configured to receive a coolant having a temperature which is increased while passing through the at least one electrical component; wherein a first end portion of the first connection line is connected to the coolant line through the first valve and a second end portion of the first connection line is connected to the heater, wherein a first end portion of the second connection line is connected to the branch line between the second valve and the chiller and a second end portion of the second connection line is connected to the heater, and wherein the heater is mounted inside the HVAC module. a cooling apparatus including a radiator, a first water pump, a first valve, and a reservoir tank which are connected through a coolant line, to circulate a coolant in the coolant line to cool at least one electrical component mounted in the coolant line; a battery cooling apparatus including a battery coolant line connected to the reservoir tank through a second valve, and a second water pump and a battery module which are connected through the battery coolant line to circulate the coolant in the battery module; a chiller mounted in a branch line which is connected to the battery coolant line through the second valve and connected to a refrigerant line of an air conditioner through a refrigerant connection line, to adjust a temperature of the coolant by performing heat exchange between a coolant which is selectively supplied to the branch line and a refrigerant which is selectively supplied from the air conditioner, wherein the air conditioner includes a heating, ventilation, and air conditioning (HVAC) module; and a heating circuit including a heater which is connected to the coolant line and the branch line through first and second connection lines configured to receive a coolant having a temperature which is increased while passing through the at least one electrical component; wherein a first end portion of the first connection line is connected to the coolant line through the first valve and a second end portion of the first connection line is connected to the heater, wherein a first end portion of the second connection line is connected to the branch line between the second valve and the chiller and a second end portion of the second connection line is connected to the heater, and wherein the heater is mounted inside the HVAC module.