The title hydrate, [Mo(2)Cl(2)O(5)(C(18)H(24)N(2))(2)]·0.2H(2)O, has been isolated as the oxidation product of [Mo(η(3)-C(3)H(5))Cl(CO)(2)(di-t-Bu-bipy)] (where di-t-Bu-bipy is 4,4'-di-tert-butyl-2,2'-bipyridine). A μ-oxide ligand bridges two similar MoCl(di-t-Bu-bipy)O(2) units, having the terminal oxide ligands mutually cis, and the chloride and μ-oxide trans to each other. In the binuclear complex, the coordination geometries of the metal atoms can be described as highly distorted octa-hedra. Individual complexes co-crystallize with a partially occupied water mol-ecule of crystallization (occupancy factor = 0.20; H atoms not located), with the crystal packing being mediated by the need to effectively fill the available space. A number of weak C-H⋯O and C-H⋯Cl inter-actions are present.