In this paper, the technology for obtaining  polypropylene (PP) based composite materials reinforced with functionalized glass fibers (GF) is described. In the first step, glass fibers were functionalized by hydrolysis/condensation with (3-aminopropyl) trimethoxysilane as functionalization agent and in the second step, these materials were compounded at 180^oC in a Brabender mixer with isotactic polypropylene. The obtained composites were morphologically and structurally characterized by X ray diffraction (XRD), infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). Based on the obtained results it can be concluded that GF functionalization leads to a better glass fiber - polymer interaction, GF being covered by an intimate PP film.