The power dissipated in computer chips has been growing with each new technology node reaching unsustainable levels. In such a situation, the search for materials that conducts heat well and fast became essential for design of the next generations of integrated circuits (ICs) and three-dimensional (3D) electronics . Efficient thermal management of electronics, optoelectronics and photonic devices require better thermal interface materials (TIMs). Current TIMs are based on polymers or greases filled with thermally conductive particles such as silver or silica, which require high volume fractions of filler (up to 70%) to achieve K of ~1-5 W/mK of the composite. Carbon materials such as carbon nanotubes (CNTs) have been studied as possible fillers in TIMs. Theoretical and cost considerations suggest that chemically derived graphene and few-layer graphene (FLG) flakes can perform better than other carbon materials in TIMs. It was discovered that the intrinsic thermal conductivity of graphene is extremely high . At the same time, thermal properties of graphene flakes in the composites will be determined by the flake size, thickness, and coupling to the matrix material. We report the results of the experimental investigation of thermal properties of the graphene reinforced composite materials. The TIM samples were produced using the chemically derived graphene and FLG flakes. The number of atomic planes in FLG flakes was determined with the micro-Raman spectroscopy . Thermal properties of the resulting graphene-epoxy composites were measured with the “laser flash” and “hot disk” thermal conductivity techniques. The thermal conductivity enhancement factor exceeded ~ 2300% at 10% of the volume loading fraction. To achieve such strong enhancement with the conventional filler materials one would need a loading fraction of ~70%. The computer simulations of thermal properties of TIM composites carried out using the modified effective medium approximation, which included the thermal boundary resistance effects, were in agreement with our experimental data. Our results suggest that graphene and FLG flakes can become excellent filler materials in the next generation of TIMs. The work at UCR was supported, in part, by the Office of Naval Research (ONR) award on Graphene Quilts for Thermal Management of High-Power Density Electronics and DARPA – SRC through the FCRP Center on Functional Engineered Nano Architectonics (FENA).