A simple and effective electrochemical sensor was designed by the drop cast method for the detection of Diclofenac Sodium (DS), a widely used painkiller, by combining the significant catalytic property of multi-walled carbon nanotubes (MWCNTs), excellent adsorption capacity and film forming ability of Chitosan and synergistic catalytic effect of Chitosan-copper complex. The characteristics of newly proposed composite (MWCNTs/CTS-Cu/GCE) were investigated by different techniques like Fourier Transform Infrared Spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM) and Energy dispersive X-ray analysis (EDX). The electrochemical performance of the newly modified composite was studied by using Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), Square wave voltammetry (SWV). Under the optimum conditions, the anodic peak current for Diclofenac sodium (DS) was linear and the range is between 0.3 and 200 mu mol L-1 with the detection limit of 0.021 mu mol L-1 at pH 4.0. Finally, this modified composite exhibit good selectivity, sensitivity and stability for the detection of Diclofenac sodium (DS) from the pharmaceutical dosage form and real samples. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.