A simple and convenient method is described for voltammetric determination of thiamazole, a commonly used anti-hyperthyroid drug, based on its electrochemical oxidation at a multi-wall carbon nanotube modified glassy carbon electrode. Under optimized conditions, the proposed method exhibited acceptable analytical performances in terms of linearity (over the concentration range from 1.0 9 10 -7 to 5.0 9 10 -4 mol L -1 , r = 0.9983), detection limit (3.0 9 10 -8 mol L -1 ) and reproducibility (RSD = 2.64%, n = 10, for 5.0 9 10 -5 mol L -1 thiamazole). To further validate its possible application, the method was used for the quantification of thiamazole in pharmaceutical formulations and biological fluids.