An in situ plated bismuth-film electrode (BiFE) was used for the study of the herbicide pendimethalin. A single peak was observed by cyclic voltammetry at -0.520 V associated with the reduction of pendimethalin in HCl solution at pH 3.0. Square-wave cathodic voltammetry (SWCV) was used for the analytical procedures after the preparation of the BiFE using 10.0 mmol L-1 Bi(III) for 80 s at -0.250 V. A peak current at -0.585 V related to the reduction of the herbicide was obtained, which increased linearly with the pendimethalin concentration in the range of 0.3 to 1.0 mmol L-1. The limit of detection attained was 37.0 nmol L-1. The sensor prepared in situ was applied for the determination of pendimethalin in simulated samples of tap water and sea water with satisfactory results being obtained compared with the UV-vis spectroscopy technique. In addition, pendimethalin was spiked and determined at nanomolar level in samples of water collected from a local river. The recovery values for such experiments were between 93% and 96%. (C) 2015 Elsevier Ltd. All rights reserved.