PP/EPR binary and PP/(EPR/PE) ternary blends were prepared based on the viscosity ratio, using a corotating twin-screw extruder. Both fibrillar structures and particle-in-matrix morphologies were created depending on the viscosity ratio of rubber domain to the matrix PP(eta(EPR)/eta(PP), Or eta(EPR-PE)/eta(PP)) With fibril formation, mechanical properties of the blends, especially the flexural modulus and notched impact strength, were significantly increased and the increase was more pronounced with the ternary blends. The fractured surfaces obtained from the impact test showed compressed welded grains for fibrillar morphology and filled-out particles for particle-in-matrix morphology.