In the title compound, [Mo(2)(C(2)O(4))O(4)(C(6)H(6)N(4))(H(2)O)(2)]·3H(2)O, the coordination polyhedra for both Mo(V) atoms consist of two bridging O atoms, two atoms of the chelating ligand (oxalate or diimidazole), a terminal O atom and one H(2)O mol-ecule. The two distorted octa-hedrally coordinated Mo(V) atoms are linked together via O-O edge-sharing and Mo-Mo inter-actions with a Mo-Mo bond length of 2.564 (5) Å. Uncoordinated water mol-ecules are situated in the voids of the crystal structure. N-H⋯O and O-H⋯O hydrogen bonding between the neutral mol-ecules and the water mol-ecules lead to a consolidation of the structure.