A simple and super selective electrochemical sensor based on carbon microfibers C mu F coated with Nafion (Naf) and silver nanoparticles composite (C mu F/Ag NPs-Naf) to detect hydrogen peroxide is proposed. Nafion was used as an ionic conducive substrate on the surface of C mu F and silver nanoparticles (Ag NPs) were electrochemically deposited on the C mu F. The sensor showed an excellent detection performance toward H2O2. Field emission scanning electron microscopy (FESEM) and energy dispersive x-ray analysis (EDX) were used to confirm the formation of silver nanoparticles on the carbon microfibers under Nafion matrix. The electrocatalytic behaviors of this sensor were also studied by cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). Using amperometric method and under optimal conditions, a fast response of < 1 s was observed. The response of the sensor was proportional to the H2O2 concentration in a range of 0.10-80.00 mM (R-2 = 0.997) with a detection limit of 0.48 mu M. In the (EIS) method, two linear ranges of 2.0-10 mM and 10.0-100 mM were attained. The accuracy of this sensor was successfully tested with a commercial mouthwash solution. Flexibility, rapid response, low detection limit, high selectivity, wide linear range, cost-effectiveness and high sensitivity of this sensor in both amperometric and (EIS) studies make it valuable as an excellent non-enzymatic H2O2 sensor.