In this work we carry out a multifunctional property study on functionalised GNP-epoxy nanocomposites. We use commercial grade GNPs, functionalised using scalable and effluent-free plasma treatment, to prove industrial suitability. We plasma treat the GNPs using two different process gases, CF4 and NH3. Then characterise these functionalised GNPs to evaluate their new surface chemistries and any changes in particulate morphology. These are used, alongside the baseline material, to produce GNP epoxy nanocomposites. The mechanical, thermal, and electrical properties of the different nanocomposites are evaluated across a range of filler loadings, and the dispersion of GNPs in the matrix examined using SEM. The effects of the different filler surface chemistries on the multifunctional properties of GNP epoxy nanocomposites are then discussed.