In order to evaluate the compatibilizing effects of isocyanate (NCO) functional groups on ethylene vinyl alcohol copolymer/high density polyethylene (EVOH/HDPE) blends, HDPE grafted with 2-hydroxyethyl methacrylate-isophorone diisocyanate (HDEP-g-HI) was prepared and blended with EVOH. The grafting was confirmed by infrared spectra, and the grafting ratio was 4.9% from elementary analysis. From the morphologies of EVOH/HDPE-g-HI blends, it was found that an improved adhesion between the two components and finer dispersions were produced as a result of chemical reactions occurring during the melt blending. The depression of melting temperature of EVOH in the 10/90 EVOH/HDPE-g-HI blend indirectly indicated increased miscibility. The tensile strength of the EVOH/KDPE-g-HI blend was much higher than that of the EVOH/HDPE blend having no adhesion at each composition, and a dramatic increase in the impact strength was produced at the 90/10 EVOH/HDPE-g-HI blend composing of the fine HDPE-g-HI dispersions.