A novel electrochemical sensor for the detection of hydrogen peroxide (H₂O₂) is proposed based on carbon supported Pt-MnO_x and Pt nanoparticles, successfully synthesized via microwave irradiation polyol method. The physicochemical properties of the Pt-MnO_x and Pt nanoparticles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Transmission electron microscopy (TEM). Electrochemical properties of the nanoparticles were investigated by cyclic voltammetry (CV) and chronoamperometry (CA). Electrochemical measurements indicate that the oxidation current of H₂O₂ is linear (R²=0.998) to its concentration from 2 μM to 4.0 mM with a detection limit of 0.7 μM (signal/noise = 3). In addition, Pt-MnO_x is not affected by ascorbic acid (AA) and uric acid (UA) which are common interfering species. Meanwhile, this Pt-MnO_x non-enzymatic H₂O₂ sensor exhibits excellent selectivity, stability and reproducibility. Thus, this novel non-enzymatic sensor can be found practical applications in H₂O₂ detection.