Electronic structure, elastic constants and thermodynamic properties of Mg2Sn have been calculated by using the first-principles pseudopotential method. As shown by the calculated results, the band gap of Mg2Sn is 0.1198 eV. The linear response method is applied to determine the phonon dispersion relations and phonon density of states. The thermodynamic properties such as the constant-volume specific heat and Debye temperature are calculated. The calculated thermal conductivity is compared with the experimental data.