A new vanadium antimony selenite, VSb(SeO3)(4), has been synthesized through a solid-state reaction by using V2O5, Sb2O3, and SeO2 as reagents. The crystal structure of VSb(SeO3)(4) has been solved and refined by single-crystal X-ray diffraction. Whereas the starting V5+ cation has been reduced to V3+, the Sb3+ cation has been oxidized to Sb5+ during the synthesis. VSb(SeO3)(4) has a three-dimensional framework structure consisting of V/SbO6 octahedra and SeO3 groups. The V3+ and Sb5+ cations are statistically disordered in the same site with 50% occupancy. The oxide ligands in SeO3 groups are shared by V/SbO6 octahedra, and the framework expands outward radially from the center. The effective magnetic moment is estimated to be mu(eff) = 2.57 mu(B) per V3+ from the magnetic property measurements. The g-factor is determined to be g = 1.9(4) from the electron paramagnetic resonance spectrum, which is typical for a d(2) ion. The spin-polarized DFT+U calculations with U = 4 and 5 eV exhibit the magnetic moments of 1.98 mu(B) and 2.01 mu(B), respectively, on V3+ ion. Infrared and UV-vis diffuse reflectance spectra, elemental analysis, X-ray photoelectron spectroscopy, thermal analysis, and electronic structure calculations are also reported.