A highly sensitive non-enzymatic glucose sensor based on Cu nanoparticles (CuNPs)/polyaniline (PANT)/graphene nanocomposite was fabricated via simple in-situ reduction of Cu precursor in polyaniline nanofibers under mild conditions followed by mechanical mixing with graphene suspension to form the composites with different graphene contents (0.5%, 1%, and 2%). The properties of nanocomposites were characterized by SEM, TEM, XRD, UV-Vis, and XPS. The CuNPs (d = 2-4 nm) only slightly altered the ordered structure of PANI. It was found that CuNPs have direct electronic interaction with PANI via the N atoms on the polymer backbone, which enabled fast electrons transfer from electrode to CuNPs through graphene and PANI. The CuNPs/PANI/graphene nanocomposites were coated on a glassy carbon electrode for the investigation of their electrochemical properties. Both CuNPs/PANI and CuNPs/PANI/graphene showed high sensitivity towards glucose oxidation which occurred at similar to 0.5 V vs. SCE. The best performance was achieved by the CuNPs/PANI/1% graphene-modified electrode which showed sensitivity of similar to 150 mA cm(-2) M-1, detection limit of 0.27 mu M (S/N = 3), and response time of about 3 s. This system was also highly selective towards glucose oxidation that almost no signal was detected from interferents such as ascorbic acid and dopamine, demonstrating its great potential as a non-enzymatic glucose sensor. (C) 2016 Elsevier B.V. All rights reserved.