The complete polyoxidometallate anion in the title compound, (CH6N3)4[H6V4As6O30]·4H2O, is generated by crystallographic inversion symmetry. The polyhedral building units are distorted VO6 octa-hedra and AsO3OH tetra-hedra. The VO6 units feature a short formal V=O double bond and are linked by a common edge. Two such V2O6 double octahedral units are linked by four isolated AsO3OH tetra-hedra to complete the anion, which features two inter-nal O-H⋯O hydrogen bonds. In the crystal, O-H⋯O hydrogen bonds between the polyoxidometallate anions generate (01-1) sheets. The sheets are connected by cation-to-cluster N-H⋯O hydrogen bonds, and cation-to-water N-H⋯O links also occur. The O atom of one of the water mol-ecules is disordered over two sites in a 0.703 (17):0.297 (17) ratio.