[en] A polycrystalline Mg₂Sn thin film has been prepared by thermal co-evaporation in ultrahigh vacuum of Mg and Sn onto a naturally oxidized Si(100) substrate at -140 C. The structure of the sample was characterized by X-ray diffraction (XRD) and ¹¹⁹Sn conversion electron M(umlt o)ssbauer spectroscopy (CEMS). The semiconducting property of the Mg₂Sn thin film was confirmed by electrical resistance, magnetoresistance, Hall-effect and infrared spectroscopy measurements, and a value of ∼0.2 eV was found for the electronic gap energy. The ¹¹⁹Sn-projected partial vibrational density of states (VDOS), g(E), has been measured by nuclear resonant inelastic X-ray scattering (NRIXS) of 23.878 keV synchrotron radiation. Together with g(E), other thermodynamic quantities such as the probability of recoilless absorption (f-factor), the average kinetic energy per Sn atom, the average force constant, and the vibrational entropy per Sn atom are obtained. The partial VDOS of both elements (Mg and Sn) has been calculated theoretically and reasonable agreement with the measured ¹¹⁹Sn-projected VDOS is observed. g(E) is characterized by a phonon energy gap ranging from ∼17 to ∼21 meV