Ferrite of system, namely Ni 1− x Zn x Fe 2 O 4 with x=(0.0,0.2,0.4,0.6,0.8,1.0), have been prepared by solid state reaction to investigate the effect of gamma rays irradiations using Co 60 source on the cation distribution, structural and magnetic properties. The unirradiated and irradiated samples were then subjected to characterization techniques such as X-ray diffraction, magnetization and AC susceptibility. The results of these characterizations are found to be different for irradiated from that of the pristine sample. The modifications in respect of irradiated samples are explained in terms of the ion-induced disorder. The important result of γ-irradiation on the cation distribution, structural and magnetic properties is the change of ratio Fe 2+ /Fe 3+ . Possible reasons on the results are proposed.