A novel thermomechanical exfoliation method of expanded graphite is used to produce few-layer graphene nanoplatelets (GNP). Following detailed characterization using Raman spectroscopy, X-Ray diffraction and microscopy, the GNP is then used to produce polypropylene (PP) nanocomposites by melt compounding. The resulting composites show a high degree of reinforcement and an electrical percolation threshold of about 0.5 vol% of GNP. Using a batch foaming technique, we further develop composite foams with fine microcellular morphology and well-controlled cell size in the range of 20 – 60 μm. Cell formation via a secondary nucleation step results in bimodal size distribution. The compressive moduli of the resulting composite foams containing 3 wt%, 9 wt% graphene nanoplatelets are 5 times and 10 times higher than unfilled foam, respectively.