This research explores the potential of using exfoliated graphite nanoplatelets, xGnP, (graphene sheets ∼10 nm thickness, ∼1 μm diameter), as reinforcement in polypropylene, PP. xGnP–PP nanocomposites were fabricated by melt mixing and injection molding. The feasibility of using xGnP–PP nanocomposites was investigated by evaluating the flexural strength, modulus and impact strength and studying the morphology of this system as a function of xGnP loading and aspect ratio and by comparing the xGnP–PP with composites made with commercial available reinforcements such as carbon fibers, carbon black and clays. It is concluded that the smaller aspect ratio xGnP has the strongest impact on the mechanical properties of PP, at loadings up to 5 vol.%, compared to the other reinforcements used, which reflects the compatibility between the exfoliated graphite nanoplatelets and the PP matrix and the exceptional mechanical properties of xGnP, similar to crystalline graphite.