The initial stages of chemical vapor deposition of TiSi2 from TiCl4, H-2, and Si(100) have been investigated with respect to the phase formation sequence. The result showed that the metastable C49 TiSi2 phase was formed prior to the equilibrium C54 TiSi2 phase. As the growth continued, the C49 phase was transformed to the C54 phase. X-ray diffraction analyses showed that both TiSi2 phases exhibited an epitaxial-like growth with respect to the substrate. Moreover, the transformation from the C49 phase to the C54 phase was favored by increased film thickness rather than high-temperature annealing. The results could be explained by an interfacial stabilization effect where the metastable C49 phase is stabilized by epitaxy. In addition, the influence of oxygen and carbon on the process was investigated by adding O-2 and C2H4 to the reaction gas mixture. Oxygen had no effect while a minor stabilization of the C49 phase was observed when carbon was introduced during deposition.