The simultaneous determination of two pesticides, namely isoproturon and carbendazim, by single drop analysis using a graphene-based electrochemical sensor with square wave stripping voltammetry was developed. A 60 mu L aliquot of the test sample was applied onto the sensor and analyzed, where clear electro-oxidation peaks from the isoproturon and carbendazim were detected. After the assay conditions were optimized by univariate analysis of the amount of graphene, type and concentration of supporting electrolyte, applied sample volume, accumulation potential and time, square wave frequency, step potential and amplitude, then the analytical characteristics were then evaluated. The oxidation peak currents varied linearly for concentrations over 0.02-10.0 mg/L (R-2 = 0.9991) for isoproturon and 0.50-10.0 mg/L for carbendazim (R-2 = 0.9990). The detection limits (3S(b)/S) were 0.02 and 0.11 mg/L for isoproturon and carbendazim, respectively. The proposed method could be applied to determine the isoproturon and carbendazim concentrations in water, soil and vegetable samples, where the recoveries of the spiked samples were acceptable (81.4-107%) and the results were statistically similar to those obtained from the standard HPLC-UV method. Therefore, the proposed method showed a great promise as an inexpensive and simple sensor, with additionally a shorter analysis time. (C) 2014 Elsevier B.V. All rights reserved.