An electrochemical sensing platform made of chitosan stabilized silver nanoparticles was synthesized as a modifier of carbon paste electrode for the determination of thiamethoxam. The obtained electrode denoted CHI-AgNPs/CPE exhibited the best electron transport characteristics for thiamethoxam electroreduction with respect to other electrodes studied including CHI/CPE and CPE. The electroanalytical performances were assessed by square wave voltammetry. The calculated limit of detection and quantification were 9.32 × 10−7 mol L − 1 and 3.10 × 10−6 mol L − 1, respectively, with a wide linear range of 4.0 × 10−6 to 1.0 × 10−3 Mol L − 1. Therefore, the proposed electroanalytical procedure was successfully used to determine thiamethoxam insecticide in Zea mays and Phaseolus Vulgaris L. plants, yielding satisfactory results.