In this work, ultra-strong, lightweight, and thermally conductive hybrid polypropylene-based composites reinforced with graphene nanoplatelets (GnP) and glass fibre (GF) were fabricated and characterized;​ demonstrating their ability to be tailored for high-performance applications in the automotive industry. GnPs expedited the crystallization of the polymer matrix by serving as seeds for heterogeneous nucleation, while inducing β-crystals. The hybrid composites yielded improved properties greater than the sum of the properties of the individual reinforcing materials, showing a synergistic effect. The synergistic effect was maximized with 0.5wt.% GnP and increased with lower concentrations of GF, whereby the greatest effect was approximately 54% and 65% for the Tensile and Flexural Modulus, and 37% and 39% for the Tensile and Flexural Strength, respectively. Moreover, an 18% weight reduction was achieved with PPGnP0.5GF40 while maintaining the desirable mechanical strengths of PPGF60. Furthermore, the thermal conductivity was maximized with PPGnP5GF50, exceeding that of Neat PP by 201%.