The growth rate of ion‐cyclotron waves, parametrically excited by a pump magnetic field oscillating in time in a hot plasma, is calculated. The process occurs through the excitation of a slow ion‐cyclotron wave and a fast wave propagating in opposite directions along the magnetic field, as has been found previously for the case of a cold plasma. The growth rate of the waves is found to vanish at a critical temperature, that temperature being higher for a lower value of the ratio of the pump frequency to the ion‐cyclotron frequency. Below the critical temperature the growth rate is always less than the cold plasma growth rate.