Rheology, dynamic mechanical properties, mechanical properties, and morphology of ethylene-propylene-diene rubber/butadiene rubber (EPDM/BR) blends with or without a homogenizing agent or a coupling agent were investigated. AAHR (a mixture of aliphatic and aromatic hydrocarbon resins) was used as a homogenizing agent and bis(3-triethoxysilyl propyl)tetrasulfide (TESPT) was used as a coupling agent. The dynamic mechanical analysis and the morphological studies revealed that EPDM and BR were incompatible and the addition of AAHR was very effective to plasticize the EPDM/BR blend and enhance the compatibility between EPDM and BR. It was found that the addition of an AAHR increased the amounts of bound rubbers and, hence, the vulcanizate properties such as tear strength and fatigue resistance of the EPDM/BR blends were improved. The blends of maleic anhydride-grafted EPDM and BR were also prepared and the properties were compared. The dynamic mechanical analysis and the morphological studies revealed that the addition of TESPT increased the weight of bound rubbers and provided better dispersion of carbon black, resulting in good mechanical properties such as tear strength and fatigue resistance of the vulcanized EPDM/BR blends.