A novel electrochemical sensor based on poly(diallyldimethylammonium chloride) (PDDA) functionalized graphene (PDDA-G) composite film has been developed for the detection of 4-nitrophenol (4-NP). The PDDA-G was successfully prepared and characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Due to PDDA-G has more functional groups which were beneficial for the absorption of 4-NP by electrostatic interaction, it was found that the sensitivity for 4-nitrophenol was remarkably improved at the PDDA-G nanocomposite film modified GCE. The experimental parameters such as the pH of buffer solution, the scan rate, the accumulation time and potential were optimized. Under the optimum experimental conditions, this sensor had a wide linear range over 4-NP concentration from 0.06 mu M to 110 mu M with a detection limit of 0.02 mu M (S/N = 3). Furthermore, the PDDA-G sensor not only exhibited good stability with adequate reproducibility and accuracy, but also demonstrated efficiency in the detection of 4-NP in water samples. It was expected that this method has great promise for simple, sensitive, selective detection of 4-NP. (C) 2014 Elsevier B.V. All rights reserved.