In this study, PP-based composites reinforced were produced by using three injection pressures I P (50, 55, 60 MPa), three injection temperatures I T (210, 220, 230 °C), three holding pressures H P (35, 40, 45 MPa), three reinforcement rates R r (5, 10, 15 wt.-%) and three reinforcement sizes R s (44–100, 101–210, 210–300 μm) and their mechanical properties were investigated. Moreover, 0.2 % maleic anhydride was also added in order to prevent oxidation during addition of aluminum powders. The best results in terms of tensile strength were obtained from the specimen with the code C2, with the parameter values R s = 100 – 210 μm, R r = 15 wt.-%, I T = 230 °C, I P = 50 MPa and H P = 40 MPa. The best results in the tensile tests were received from the specimen with code A2, having the parameter values R s = 100–210 μm, R r = 5 wt.-%, I T = 210 °C, I P = 50 MPa and H P = 35 MPa. On the other hand, the best results in the izod tests were obtained for the specimen with the code C1 with the parameter values R s = 44–100 μm, R r = 15 wt.-%, I T = 210 °C, I P = 60 MPa and H P = 45 MPa.