A careful experimental and theoretical study of the double perovskite type material Ba2YSbO6 is reported. The results show that this yttrium-based antimoniate oxide crystallizes in a cubic structure, Fm3¯m (#225) space group, with evidence of the cationic ordering that characterizes a rocksalt superstructure, and tolerance factor slightly less than the unit (τ = 0.9791) due to the size differences between the Y-O6 and Sb-O6 octahedrons. The magnetic response shows weak ferromagnetic effects for the temperature values studied (50, 200 and 300 K), with evidence of an antiferromagnetic reentrance at T = 118 K under the application of low magnetic fields, which is attributed to the presence of polar ordering, accompanied by octahedral distortions caused by the movement of the cations Y3+ and Sb5+, whose effects are no longer observed in the presence of a fairly high external magnetic field (of the Tesla order). The results of the optical characterization by diffuse reflectance suggest the occurrence of a band gap Eg = 4.61 eV, which is characteristic of an insulating material. The electronic structure calculations corroborate the insulating nature of the Ba2YSBO6 complex perovskite. The results allow classifying this material as a Mott insulator, in which the occurrence of intra-site spin-exchange facilitates unpaired spins to the 4d-t2g Yttrium states, mediated by the 2p Oxygen orbitals and 5p Antimony orbitals, resulting in the ferromagnetic character of the insulating material.