Clinoptilolite nanoparticles (NClin) were Fe(ll)-exchanged and used for the modification of carbon paste electrode (Fe(II)-NClin-CPE) in indirect determination of iodate. The voltammetric peak current of Fe(II)/Fe(III) redox system was decreased in the presence of iodate in solution. Sufficient characterization was applied for the raw and modified zeolite and CPE. The electrochemical impedance spectroscopy (EIS) confirmed that Fe(II)-NClin/CPE had the best charge transfer ability with respect to the raw CPE and NClin/CPE. The simultaneous effects of the most important influencing variables of square wave voltammetry (modifier%, solution pH, step potential and amplitude) were studied by designing the experiments by using response surface methodology (RSM). The optimal run obtained at pH 2.18, amplitude = 0.472 V, modifier% = 17.5 and step potential = 0.0202 V. Under the optimum conditions, the current response of Fe(II)-NClin/CPE was inversely proportional to IO3- concentration in the range of 4-100 mu mol L-1 with a detection limit of 0.64 mu mol L-1. Capability of the modified electrode for the determination of iodate in iodofolic pharmaceutical tablet was studied and the obtained results were statistically compared with the results obtained by iodometric titration as a standard method.