In recent years, blend technologies have been developed to modify mechanical properties of polypropylene by dispersing discrete stress-concentrating polyamide microparticles in the continuous polypropylene matrix. The work presented here is concerned with the examination of fundamental relationships between blend morphologies and mechanical properties, especially plastic deformation mechanisms at high strain. Polyamide-6, polyamide-12, polyamide-12 plasticized with N-butyl-phenylsulfonamide, and polyamide-6 in situ embedded in a shell composed of polyamide-36,6 have been used as blend components in polypropylene blends containing 30 vol % of these polyamides. For modification of interfacial adhesion, maleic-anhydride-grafted-polypropylene has been added. When the yield stresses of polyamide and polypropylene are matched, large elongations at break of the resulting blends can be achieved. The influence of crazing, voiding, and shear yielding has been elucidated by transmission electron microscopic analysis of strained blend samples.