Poly(vinyl chloride) (PVC)composites were prepared by compounding different concentrations of antimony trioxide Sb2O3 (ATO) and Organo-modified montmorillonite clay (OMMT) as fillers under the effect of gamma irradiation in order to improve its fire retardancy properties. The fire retardacny of the prepared PVC composites were evaluated by measuring ofthe limiting oxygen index (LOI). The mechanical properties, thermal stability by using of the thermogravimetric analysis (TGA) and the electrical conductivity were also investigated. The results indicated that the addition of ATO alone up to 3 phr or the mixture of ATO 1.5 phr/ OMMT 1.5 phr enhances the fire retardancy properties, accompanied with a decrease in the mechanical properties, without effective change in the thermal and electrical conductivity. Moreover, it was found that the mechanical properties and the gel content of the prepared PVC composites were enhanced accompanied with a decreasing in the swelling ratio, as a function of the irradiation with gamma rays up to 50 kGy.