A series of 4-t-butyl styrene-g-ethylene propylene diene monomer (EPDM) (t-BS-g-EPDM) gels was prepared by direct gamma ray irradiation with varying contents of t-BS in EPDM. Characterization of irradiated t-BS-g-EPDM gels was performed by Fourier transform infrared (FTIR) spectroscopy, tensile tests, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and oil absorbency tests. It was observed that the increment in irradiation dose up to 90 kGy would increase the percentage of gel content due to the increase in crosslink density. Tensile properties of t-BS-g-EPDM gels increased with the introduction of irradiation up to 150 kGy except for elongation at break. The section picture of t-BS-g-EPDM gels by SEM showed a homogenous and smooth surface, indicating no phase separation upon irradiation. The t-BS-g-EPDM gels exhibited high swelling ability in organic solvents, and the maximum values of oil absorbency to chloroform and diesel oil were 42.3 g g⁻¹ and 23.6 g g⁻¹, respectively. These results indicated that the properties of t-BS-g-EPDM gels have been improved by irradiation with respect to an irradiated EPDM sample.