High quality Mg2Si films were grown on Si (111) and glass substrates with magnetron sputtering, respectively. The first observation of Photoluminescence (PL) of Mg2Si films was reported. The Mg2Si PL emission wavelengths are almost independence on temperature in the range of 77–300 K. The strongest PL emissions may be attributed to interstitial Mg donor level to valence band transitions. The activation energy of Mg2Si is determined from the quenching of major luminescence peaks.