The investigations of bismuth halide chemistry in DMSO/MeOH solutions led to the discovery of a new solvent-stabilized compound with a chemical formula of Cs3BiBr6.3DMSO. In addition, a new phase of Cs3BiBr6 was generated as a result of a crystal-to-crystal transition driven by the change in the solvent composition. The solvent stabilized Cs3BiBr6.3DMSO adopts an orthorhombic P2(1)2(1)2(1) type crystal structure with unit cell dimension of a = 13.6160(6) angstrom, b = 14.4359(8) angstrom, and c = 14.6487(7) angstrom. Bulk single crystals of Cs3BiBr6.3DMSO with average size of 4.5 X 3.5 X 3.5 mm(3) were grown by the antisolvent crystal growth method. With the change of the solvent composition from 2:1 DMSO: MeOH to 1:1 DMSO: MeOH, the single crystals of Cs3BiBr6.3DMSO underwent a crystal-to-crystal transition yielding another structurally distinct Cs3BiBr6 phase, with a tetragonal P4(2)/m type structure and unit cell dimensions of a = 9.8394(5) angstrom, b = 9.8394(5) angstrom, and c = 8.0950(6) angstrom. Both compounds exhibit isolated BiBr6 octahedral resembling the structures of the zero-dimensional (0D) perovskites.