The work considered the growth, optical properties and emerging interband transitions in Ca2Si films grown on silicon substrates with (111), (001), and (110) orientations at two temperatures (250 °C and 300 °C) using the sacrificial-template method. The optimum temperature for MBE single-phase growth of Ca2Si is 250 °C. Calculations of optical functions from the transmission and reflection spectra were carried out within the framework of a two-layer model and by the Kramers–Kronig method. It is shown that the main peaks in the experimental reflection spectra and the optical conductivity calculated according to Kramers–Kronig are in good agreement with each other. Comparison of ab initio calculations of the energy band structure and optical properties of a Ca2Si single crystal and two dimensional Ca2Si layers with experimental data in the region of high energy transitions showed good coincidence.