Mesoporous silica thin films encapsulating a molecular iron-triazole complex, Fe(Htrz)3 (Htrz = 1,2,4,-1H-triazole), have been generated by electrochemically assisted self-assembly (EASA) on indium-tin oxide (ITO) electrode. The obtained modified electrodes are characterized by well-defined voltammetric signals corresponding to the Fe II/III centers of the Fe(Htrz)3 species immobilized into the films, indicating fast electron transfer processes and stable operational stability. This is due to the presence of a high density of redox probes in the material (1.610-4 mol g-1 Fe(Htrz)3 in the mesoporous silica film) enabling efficient charge transport by electron hopping. The mesoporous films are uniformly deposited over the whole electrode surface and they are characterized by a thickness of 110 nm and a wormlike mesostructure directed by the template role played by Fe(Htrz)3 species in the EASA process. These species are durably immobilized in the material (they are not removed by solvent extraction). The composite mesoporous material (denoted Fe(Htrz)3@SiO2) is then used for the electrocatalytic detection of hydrogen peroxide, which can be performed by amperometry at an applied potential of-0.4 V versus Ag/AgCl and by flow injection analysis. The organic-inorganic hybrid film electrode displays good sensitivity for H2O2 sensing over a dynamic range from 5 to 300 μM, with a detection limit estimated at 2 μM.