The perovskite form of the Mn2FeSbO6 oxide has been obtained at 5.5 GPa and 1523 K. X-ray and neutron diffraction data reveal that this compound crystallizes in the monoclinic P21/n space group with a = 0.5234 nm, b = 0.5389 nm, c = 0.7642 nm and β = 90.372° lattice parameters. AC and DC magnetic susceptibility measurements suggest the existence of a complex magnetic behavior below 200 K. The magnetic structure has been determined and can be described on the basis of an elliptical spiral with an incommensurate propagation vector, k = [0,0.426,0], where the magnetic moments of 2Mn(2+) and Fe(3+) cations are confined to the ac-plane.