Structural and electronic properties of the Sr2MnSbO6 perovskite in cubic (Fm-3m) and tetragonal (I4m and P/4mnc) crystallographic phases have been determined using the Full Potential Linearized. Augmented Plane Waves (FP-LAPW) method, in the framework of the Density Functional Theory (DFT). The exchange and correlation effects were treated using the Generalized Gradient. Approximation plus the Hubbard term (GGA+U) approach, in order to describe the strong on-site Coulomb repulsion among the localized d-Mn electrons. The structural stability was determined by fitting of the total energy values to the Murnaghan equation of state. The values for the structural parameters are in good agreement with experimental results reported in the literature. The study of the electronic properties carried out through the graphical presentation of the densities of states for the two spin polarizations shows that the compound presents half-metallic behavior.