Polypropylene/polyamide-6 (PP/PA) blends containing maleic anhydride grafted elastomers were prepared by reactive blending. Three different types of core shell morphologies were obtained and characterized by transmission electron microscopy (TEM). The modulus of these elastomer modified PP/PA (70/30) blends with core shell type morphology is compared to predictions derived from the Kerner model. The multiphase morphology of these blends could be modeled by sequential application of the Kerner equation to two-phase subinclusions. Using morphological data obtained by TEM, good agreement between experimental and calculated values was obtained. The results are used to tailor PP/PA-6 blends combining stiffness and toughness.