The voltammetry of imidacloprid was investigated by using three kinds of carbon paste electrodes (CPEs) based on tricresyl phosphate, silicone oil, and n-tetradecane. The tricresyl phosphate-based carbon paste electrode exhibited the best analytical performance with respect to peak shape and signal intensity. The method, operated in the differential pulse voltammetric mode, was applied to the determination of imidacloprid in a river water sample and two commercial formulations and works in the concentration range from 1.7 to 30 μg mL⁻¹, with a relative standard deviation not exceeding 2.2%. This appears to be the first application of a CPE to the voltammetric determination of neonicotinoid insecticides.