A new composite electrode material consisting of Methylene Blue (as redox mediator), a synthetic NaX zeolite (as immobilization support) and carbon paste (as conductive material) was obtained and characterized. The electrochemical behavior of carbon paste electrodes incorporating Methylene Blue adsorbed on zeolite (MB-Z-CPEs) has been investigated at various pH values and potential scan rates. From cyclic voltammetry (CV) measurements, the rate constant (ks) of the heterogeneous electron transfer and the transfer coefficients (α) were estimated, using Laviron’s treatment. Finally, the electrocatalytic activity of the modified electrodes toward H2O2 reduction was investigated, using both CV and amperometric measurements. At a fixed potential (-400 mV vs. Ag| AgCl/KClsat), under magnetic stirring in phosphate buffer solution (pH 6), the calibration plot was linear over the H2O2 concentration range 8* 10-5 M to 10-3 M and the detection limit was 1.3* 10-4 M.