The title complex [(VB1)2DMFHPMo12O40·5DMF, VB1 = vitamin B1 (thiamine chloride), DMF = N,N-dimethylformamide] has been synthesized and characterized by elemental analysis, IR, UV-Vis, electron spin resonance, X-ray photoelectron spectroscopy and cyclic voltammetry methods. The X-ray crystal structure revealed that there is one independent molecule in the unit cell of the title complex that contains one mixed-valence heteropolyanion, two VB1
+ cations and six DMF molecules. The title complex possesses a centrosymmetrical arrangement in the unit cell, with the P atom at the symmetry center of the heteropolyanion and with eight O atoms surrounding the central P atom, such that two sets of PO4 tetrahedra are formed. The PO4 tetrahedra and MoO6
6−(7−) octahedra are disordered in the heteropolyanion. The bond distances of P—O
a
and Mo=O
d
are in the ranges 1.57 (4)–1.70 (4) Å and 1.61 (2)–1.67 (2) Å, respectively.