The title compound, tris-(4,4'-bipyridinium) diarsenoocta-deca-molybdate(VI), (C(10)H(10)N(2))(3)[As(2)Mo(18)O(62)], featuring protonated bipyridine mol-ecules and a classical Dawson-type polyoxo-anion, has been synthesized under hydro-thermal conditions. The polyoxoanions are linked together via the bipyridyl cations, acting as hydrogen-bond donors, generating a two-dimensional supra-molecular network. The asymmetric unit contains 1.5 4,4'-bipyridinium (H(2)bpy) units, with an inversion centre in the central bond of the second H(2)bpy unit. The site symmetry of the anion is .