The ethylene propylene diene terpolymer (EPDM)/flameretardant composites filled with aluminum hydroxide (ATH), magnesium carbonate (MgC) and zinc borate (ZnB) were prepared at different contents 15, 30, and 40 wt%, and irradiated with different gamma radiation doses, namely 50 and 100 kGy. Mechanical properties, Thermogravimetric analysis (TGA), limiting oxygen index (LOI) and swelling in motor and brake oils of the prepared composites were evaluated. Experimental results emphasized that flame resistant particles retard degradation and flammability of the composites. It has been established that the results showed that the particle size of inorganic fillers clearly have a significant effect on the whole properties of the prepared polymer composites hence zinc borate was the best. Moreover, significant alterations in characterization of polymer composites characters have been occurred due to irradiation remarkably at a dose of 50 kGy. J. VINYL ADDIT. TECHNOL., 00:000-000,