The crystral structure of tris(tetra-n-butylammonium) hydrogen hexahydroxidoplatinate(IV) [hexahydrogen α-hexamolybdoplatinate(IV)] pentadecahydrate, (C16H36N)3H[Pt(OH)6][H6PtMo6O24]·15H2O, was determined. The structural analysis revealed that all six triply-bridging O atoms of the hexamolybdoplatinate(IV) anion are protonated, making it formally the B-type Anderson anion [H6PtMo6O24]2−. The [H6PtMo6O24]2− anions connect with the [Pt(OH)6]2− anions through strong hydrogen bonds (O...O = 2.45–2.62 Å) to form a linear polymer in the crystal