This study reports an efficient method for the preparation of well-dispersed ruthenium nanoparticles of controlled size loaded into micelle-templated silica (MTS). This method is based on an organometallic approach consisting in mild decomposition of Ru(COD)(COT) (COD = g4-cycloocta-1,5-diene; COT = g6-cycloocta-1,3,5-triene) embedded inside mesostructured porous silica. The role assigned to the regular channels of MTS is to host and stabilize the metal nanoparticles. Different procedures of precursor decomposition, variation of metal loadings and of MTS pore sizes were examined in order to identify the crucial parameters governing the location, size and dispersion of the nanoparticles. The composite materials were characterized using elemental analysis, thermal gravimetric analysis, X-ray diffraction, nitrogen sorption at 77 K and TEM. The advantage of this new procedure lies in the absence of particles sintering due to the Ru reduction at room temperature and the stabilization of the nanoparticles by suitable pore size of the host.