A proposed validated square‐wave voltammetric method and high‐performance liquid chromatography, as a comparative method, are applied to measure simultaneously two metabolites‐ of current use pesticides‐ namely 3,5,6‐trichloro‐2‐pyridinol and malathion dicarboxylic acid. Method validation and quality control parameters are studied. Method detection limits are found to be 0.043 and 0.061 μg/ml for 3,5,6‐trichloro‐2‐pyridinol and malathion dicarboxylic acid, respectively whereas the practical quantification limits are found to be 0.135 and 0.193 μg/ml (voltammetry), 0.05 and 0.1 μg/ml (high‐performance liquid chromatography) for 3,5,6‐trichloro‐2‐pyridinol and malathion dicarboxylic acid, respectively. The application of the proposed method for the analysis of water samples collected from different sources has been assessed. The interaction of these metabolites with human serum albumin was studied, a 1:1 association complex was formed and their binding constants were evaluated through the calculation to be 0.30 × 102/M for 3,5,6‐trichloro‐2‐pyridinol and 8.414 × 103/M for malathion dicarboxylic acid. The low value of the binding of 3,5,6‐trichloro‐2‐pyridinol metabolite indicates that this metabolite is more likely to be more toxic than the other metabolite.