In order to improve the miscibility between the components of a blend, it is possible to modify the chemical structure by functionalizing one or more of the components. This results in better adhesion at the interface between the components and, consequently, in better mechanical properties. In this work, the influence of maleation of polypropylene on the interface between polypropylene and ethylene-vinyl alcohol copolymer was studied using the measurement of interfacial tension, surface analysis with electron spectroscopy for chemical analysis (ESCA), and morphological observation, using scanning electron microscopy (SEM). The interfacial tension between a 0.1-wt % maleated polypropylene and ethylene-vinyl alcohol copolymer was shown to be 25% lower than the interfacial tension between nonmaleated polypropylene and ethylene-vinyl alcohol copolymer. This resulted in better adhesion between maleated polypropylene and ethylene-vinyl alcohol copolymer. The surface analysis indicates that this decrease of interfacial tension is due to migration of the maleic groups of the maleated polypropylene to the interface between the 2 polymers and that, probably, a chemical interaction occurs at the interface between maleated polypropylene and ethylene-vinyl alcohol copolymer. It is also shown in this work that additives, such as SiO2, found in commercial polymers, can influence the interfacial tension between 2 polymers.