A portable communication device cooperation system includes a slave portable communication device that can communicate with a master portable communication device. Each of a plurality of slave-side slots of a slave-side storage unit included in the slave portable communication device stores a slave application program transferred from a master-side slot disposed in the master portable communication device. The slave application program includes part of information of a master application program, and causes the slave portable communication device to operate by being executed by a slave-side control unit of the slave portable communication device. As a result, the portable communication device cooperation system, the master portable communication device, and the slave portable communication device exhibit an effect of enabling the slave portable communication device to be variously used.