Clinoptilolite nanoparticles (NClin) modified with hexadecyltrimethyl ammonium bromide surfactant (HDTMABr) and Arsenazo III (ARS) was used for the modification of carbon paste electrode. The modified electrode was used for voltammetric determination of Cesium. The peak current of semi-reversible electrochemical peaks of Arsenazo III was decreased by adding cesium to the solution and hence this decrease was used for the determination of cesium in solution. The electrode response can be controlled by diffusion of cesium to the surface of the modified electrode. The modified electrode showed a suitable linear calibration graph in the concentration ranges of 8.4 x 10(-8)-1.0 x 10(-3), 9.6 x 10(-9)-1.0 x 10(-3) and 8.0 x 10(-9)-1.0 x 10(-3) mol L-1 cesium with detection limits of 3.6 x 10(-8), 3.0 x 10(-9) and 2.4 x 10(-9) mol L-1 of Cs+ for CV, SqW and chronoamperometric methods, respectively. The proposed electrode showed high selectivity for cesium among the tested cations and good recovery results confirmed applicability of the sensor for Cs determination in real samples. (C) 2016 Elsevier Ltd. All rights reserved.