The effects of the partial replacement of silica or calcium carbonate (CaCO 3 ) by bentonite (Bt) on the curing behaviour, tensile and dynamic mechanical properties and morphological characteristics of ethylene propylene diene monomer (EPDM) composites were studied. EPDM/silica/Bt and EPDM/CaCO 3 /Bt composites containing five different EPDM/filler/Bt loadings (i.e., 100/30/0, 100/25/5, 100/15/15, 100/5/25 and 100/0/30 parts per hundred rubber (phr)) were prepared using a laboratory scale two-roll mill. Results show that the optimum cure (t 90 ) and scorch (t S2 ) time decreased, while the cure rate index (CRI) increased for both composites with increasing Bt loading. The tensile properties of EPDM/CaCO 3 /Bt composites increased with the replacement of CaCO 3 by Bt from 0 to 30phr of Bt. For EPDM/silica/Bt composites, the maximum tensile strength and E b were obtained at a Bt loading of 15phr, with enhanced tensile modulus on further increase of Bt loading. The dynamic mechanical studies revealed a strong rubber-filler interaction with increasing Bt loading in both composites, which is manifested by the lowering of tan δ at the glass transition temperature (Tg) for EPDM/CaCO 3 /Bt composites and tan δ at 40 °C for EPDM/silica/Bt composites. Scanning electron microscopy (SEM) micrographs proved that incorporation of 15phr Bt improves the dispersion of silica and enhances the interaction between silica and the EPDM matrix.