A study of the dynamic complex and steady shear viscosity of isotactic polypropylene (iPP), ethylene-propylene diene terpolymer rubber (EPDM) and three different blends of both polymers are presented over a range of temperatures and frequencies. Moreover, the processability of these materials is studied through torque measurements during blend mixing. The results obtained show that the viscosity gradually increases with rubber content in the blend and decreases with both temperature and frequency. Plots of eta " versus eta ' (Cole-Cole plots) show that the blend with the lower rubber content (25%), has a certain rheological compatibility with neat PP. Furthermore, torque curves measured during blend mixing confirm these results, demonstrating that the blend with 25% of elastomer has a similar behavior of iPP during processing. To analyze the morphological structure of the blends, a dynamic mechanical analysis of the solid state is also presented. It is observed that the blends have two distinct values of T-g close to the corresponding values of the pure polymers, confirming that this type of blends based on a semicrystalline polymer and an amorphous elastomer forms a two-phase system with a limited degree of miscibility between both components. In addition, the polymer present with the higher concentration forms the continuous phase and controls the theological properties of the blend.