To provide a control valve for a variable displacement compressor, which is capable of promptly restoring the compressor to a predetermined discharge capacity even when the rotational speed of an engine is rapidly changed. In a valve section for controlling the flow rate of refrigerant flowing from a discharge chamber into a crankcase of a variable displacement compressor, a pressure-sensing section is provided in a high-pressure port that receives discharge pressure. In the pressure-sensing section, when a pressure-sensing piston which is larger in pressure-receiving area than a valve element receives a change in discharge pressure caused by a rapid change in rotational speed of the engine, differential pressure is produced between discharge pressure Pd and pressure in a pressure-adjusting chamber, which temporarily produces a force for axially moving the piston. This force is transmitted to the valve element via a shaft, to thereby accelerate the opening/closing motion of the valve element caused by the differential pressure between discharge pressure and suction pressure, whereby the compressor is promptly restored to a predetermined discharge capacity.