Pentakis(dimethylformamide-κO)oxidovanadium(IV) bis(hexafluoridophosphate), [VO(dmf)5][PF6]2 (dmf: dimethylformamide), was synthesized, and its crystal structure was revealed by a single-crystal X-ray method. The [VO(dmf)5]2+ complex cation dimerized in the crystal, and a weak ferromagnetic interaction was attributed to the dimerized structure. In addition, conformational prediction was successfully conducted using the enumeration result on the basis of group theory. As a result, a reasonable monomer structure of the defect-S 6 symmetry was obtained as the most stable structure in dilute solution; in addition, a dimer structure was predicted as the structure in a crystal.