MnSi nanoparticles on silica are prepared by metal-organic (MO)CVD of Mn(CO)5SiCl3 as a single-source precursor. Mn(CO)5SiCl3 is synthesized from Mn2(CO)10 and SiHCl3 using standard Schlenk techniques, and confirmed by Fourier transform infrared (FTIR), single-crystal X-ray diffraction (XRD), and 13C and 29Si nuclear magnetic resonance (NMR). Powder XRD patterns, high resolution transmission electron microscopy (HRTEM), elemental maps, and energy dispersive X-ray (EDX) spectroscopy show that MnSi particles, with a size of about 5–6 nm, are uniformly dispersed on the silica support. The formation mechanism of MnSi nanoparticles on silica is investigated by in-situ FTIR spectroscopy. The results demonstrate the formation details of MnSi nanoparticles from Mn(CO)5SiCl3 through the elimination of carbonyl groups and dissociation of SiCl bonds with the promotion of H2.