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.