The study of graphene nanosheet (GNS) -gold nanoparticle (AuNP)-carbon paste electrode (GNS-AuNP-CPE) as an electrochemical sensor for the determination of rivastigmine (RIV) in pharmaceuticals formulations, blood serum, and urine samples is presented. The GNS-AuNP composite is prepared by in situ simultaneous reduction of graphene oxide and chloroauric acid using sodium borohydride as a reducing agent. The GNS-AuNP composite was characterized by X-ray diffraction, UV-Vis spectroscopy, and scanning electron microscopy. Electrochemical characterization of the GNS-AuNP-CPE electrode surface was carried out by cyclic voltammetry, electrochemical impedance spectroscopy, chronocoulometry, and adsorptive stripping differential pulse voltammetiy. This study shows that oxidation of rivastigmine is facilitated at the GNS-AuNP-CPE electrode and remarkably increase in current compared to the bare electrode due to enhanced adsorption of the former on electrode surface. Under the optimized conditions, the peak current (I-p) is found to be proportional to the RIV concentration in the range of 2.0 x 10(-7)-6.0 x 10(-4) M with a detection limit of 5.3 x 10(-8) M. The proposed sensor shows a very high level of sensitivity, selectivity, and a very good reproducibility for RIV determination. A good recovery level obtained for real samples suggests practical utility of the GNS-AuNP-CPE as an effective and reliable electrochemical sensor for RIV detection. (C) 2015 Elsevier B.V. All rights reserved.