The crystallization of an amorphous TiSi2 evaporated film has been studied on both poly‐Si and SiO2 substrates. A metastable form of TiSi2 (base‐centered orthorhombic; a=3.62 A, b=13.76 A, and c=3.605 A) [P. G. Cotter, J. H. Kohn, and R. A. Potter, J. Am. Ceram. Soc. 39, 11 (1956)] is formed first at a temperature of approximately 350 °C on both substrates. This phase consumes the entire amorphous layer before undergoing a polymorphic transformation to face‐centered orthorhombic TiSi2 (a=8.24 A, b=4.78 A, and c=8.54 A) [F. Laves and H. J. Wallbaum, Z. Kristallogr. 101, 78 (1979)] at 600 and 800 °C on poly‐Si and SiO2, respectively. These transformations were investigated using in situ resistivity, x‐ray diffraction, and transmission electron microscopy. The room‐temperature resistivities observed were 96 and 20 μΩ cm for the base‐centered and face‐centered TiSi2, respectively. The enhanced polymorphic transformation on poly‐Si over SiO2 is explained by a lowering of surface energy barrier to nucleation.