A fire extinguishing system for a vehicle includes a fire detection device outputting a fire detection signal in response to detecting a fire and is installed in a predetermined space of the vehicle. A controller outputs a control signal for spraying fire extinguishing agent when the fire detection signal is received from the fire detection device. An air tank stores compressed air and a fire extinguishing agent cylinder is connected to the air tank through an air hose, is filled with the fire extinguishing agent, and is operated to discharge the fire extinguishing agent by the compressed air, supplied from the air tank through the air hose, by the control signal. A spray nozzle assembly is connected to the fire extinguishing agent cylinder through a fire extinguishing agent hose and sprays the fire extinguishing agent being supplied, from the fire extinguishing agent cylinder, through the fire extinguishing agent hose.