Electronic structure calculations and measurements of the thermoelectric properties of boron (B)-doped magnesium silicide (Mg2Si) have been performed. The calculations predict that the preferential B-doping site is an interstitial site of Mg2Si, leading to increase electron carriers. As predicted by the calculations, the prepared B-doped and non-doped polycrystalline Mg2Si samples exhibit an n-type electrical transport property. B-doping enhances the electrical conductivity and slightly lowers the absolute value of the Seebeck coefficient of Mg2Si, whereas it does not affect the thermal conductivity. Reflecting the enhancement of electrical conductivity, the dimensionless figure of merit, ZT, of Mg2Si is improved by the B-doping. Display omitted