A simple and reproducible way used to prepare hybrid inorganic-organic composite electrode materials based on polyhemin and graphene oxide (GO), consists in a drop-casting step of GO dispersed in TRIS solution on graphite followed by the simultaneously reduction of GO (rGO) and electropolymerization of hemin (polyHm). The new procedure for graphene-hemin composite preparation, preserving the intrinsic peroxidase-like activity of hemin, results in a performing G/rGO/polyHm electrode architecture. Cyclic voltammetry investigations put on evidence that the new electrode architecture displays good electrochemical parameters and excellent electrocatalytic properties towards H2O2 reduction. Square-wave voltammetry was used to plot calibration curves having analytical (linear domain between 9.9 and 50 pM of H2O2, sensibility of 61.94 +/- 6.35 mA M-1, R = 0.9958, n = 10 points, and the detection limit of 8.86 pM H2O2) and kinetic parameters (apparent Michaelis Menten constant of 20 +/- 1.45 pM H2O2) in good agreement with other previously reported values. Finally, the optimized sensor was applied to detect H2O2 in a commercial product commonly used as disinfectant. The G/rGO/polyHm electrode is thus recommended for H2O2 detection.