γ-Alumina nanoparticles have been modified with polysulfone (PSU) chains via 1,3-dipolar cycloaddition reaction between functionalized alumina with vinyl groups and terminal azide polysulfone chains of two different molecular weights. Homopolymer nanocomposites have been prepared for the first time by extrusion and microinjection. The effectiveness of the grafts on the dispersiblity has been analyzed in terms of the parameters that govern the wettability between grafted and matrix chains: graft density (σ), graft molecular weight (N) at constant matrix molecular weight (P). The dispersion state and interfacial adhesion of PSU grafted-nanoparticles have been evaluated from laser scanning confocal, FESEM and SEM microscopy. Results show that the incorporation of the modified g-alumina improves the dispersion state in comparison with bare alumina nanoparticles, reducing the average particle size from 5±9 to 1.3±1 microns. Although aggregates are still present the size of the aggregates are also substantially reduced even with low or moderate graft density used in this work, but further improves the interfacial adhesion between nanoparticle and matrix when long PSU chains are grafted even with low-moderate grafting density. These results can be explained by enthalpic compatibility between polysulfone grafted layer and host polysulfone matrix