We report on a novel technique to enhance the thermal conductivity of epoxy nanocomposites using graphene coated poly-methyl-methacrylate (PMMA) balls. PMMA balls with a diameter in the range of 200-300 nm were synthesized using suspension polymerization. These balls were coated with chemically reduced graphene oxide to form a core-shell additive and dispersed in epoxy. Thermal conductivity measurements of bulk samples of graphene-coated PMMA (GPMMA) epoxy nanocomposite were carried out and compared with baseline samples comprised of graphene nanosheets (not in the core-shell form) dispersed in the epoxy resin. Results show that the addition of 1% (by weight) GPMMA balls increases thermal conductivity by 7-fold. By contrast, the addition of 1% (by weight) of graphene nanosheets (not in the core-shell form) only improves thermal conductivity of the nanocomposite by approximately 3-fold. We attribute this improvement in thermal performance to more uniform dispersion and improved phonon conduction pathways for the GPMMA core-shell additive. Published by Elsevier Ltd.