Nanoscale mechanical properties of graphene and metal-coated graphene nanocomposite powders were evaluated using a nano-indentation method with an atomic force microscope. The obtained results were then verified using the data obtained from the first principle calculations. Graphene synthesized using the modified Hummer method showed a layered structure with a thickness of ∼ 1.1 nm. Metal coated graphene nanocomposite powders, including copper-coated graphene ones (Cu@graphene) and nickel-coated graphene ones (Ni@graphene), were synthesized using an in-situ co-reduction method. The obtained average values of Young's moduli of graphene, Cu@graphene and Ni@graphene from the nano-indentation tests were 0.98 TPa, 1.03 TPa and 1.06 TPa, and their moduli obtained using the first principle calculations were 1.051 TPa, 1.07 TPa, and 1.10 TPa, respectively. The calculated binding energy values between metal and graphene were − 1.54 eV for Cu@graphene and − 3.85 eV for Ni@graphene. Significant charge transfers between carbon atoms and metal atoms were found to apparently enhance the bond strengths of both C[sbnd]C and metallic bonds.