Removal of malathion from agricultural runoff was studied using novel copper-coated chitosan nanocomposite (CuCH)-a biopolymeric waste obtained from marine industry. Synthesis and characterization of the adsorbent using different spectral techniques like Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer, Emmett, and Teller surface analyzer have been carried out. Equilibrium studies have been carried out to optimize the dose rate, pH, and the reaction time. Parathion and methyl parathion removal were also evaluated by CuCH in the batch mode. Using gas chromatography-mass spectrometry (GC-MS) and FTIR studies suitable mechanism for adsorption has been suggested. The particle size of the adsorbent ranged from 700 to 750 nm. The surface area was found to be 20 m(2) g(-1) with a pore volume of 0.11 cc g(-1). The maximum adsorption capacity of malathion by CuCH was found to be 322.6 ± 3.5 mg g(-1) at an optimum pH of 2.0. Presence of copper ions enhanced the adsorption capacity of the adsorbent. The reaction was found to follow pseudo second-order kinetics with a rate constant of 0.53 g mg(-1) min(-1). Evidence from FTIR indicated that copper ions form a dithionate complex with malathion during the adsorption stage. The adsorbent was found to remove malathion completely from spiked concentration of 2 mg l(-1) in the agricultural run-off samples. It was also found that CuCH removed other organophospurous pesticides like methyl parathion and parathion under prevailing conditions. The results indicated that CuCH could be applied for the removal of organophosphorous pesticides.