The electrochemical determination of nonylphenol (NP) using differential pulse voltammetry (DPV) is developed based on a reduced graphene-DNA hybrid-modified glassy carbon electrode (GR-DNA/GCE). The electrochemical oxidation of NP at the GR-DNA/GCE is shown to be an one-electron and one-proton process, and due to the synergic effect of GR and DNA, the GR-DNA/GCE has 4.87, 2.76 and 2.09 times higher current response than bare GCE, DNA/GCE, and GR/GCE, respectively. Using DPV in the 0.1 mol L-1 acetate buffer solution at 0.1 V and with a 300 s accumulation time (pH = 4.6), the GR-DNA/GCE exhibits a linear current response towards the electrochemical oxidation of NP in the concentration range of 5.0 x 10(-8) to 4.0 x 10(-6) mol L-1 and a detection limit of 1.0 x 10(-8) mol L-1 (S/N = 3). In addition, this GR-DNA/GCE also indicates high selectivity and reproducibility, and can be successfully used to determine the presence of NP in Asian Clams and natural water samples with comparative sensitivity to high-performance liquid chromatography, and with recoveries ranging from 95% to 103%, showing its practical prospects in the determination of NP in real samples. (C) 2013 Elsevier B.V. All rights reserved.