The title compound, [(UO2)(2)Cl-2(OH)(2)(H2O)(4)], was obtained unintentionally as the product of an attempted reaction between uranium(VI) oxide dihydrate, UO3 center dot 2H(2)O, and hydrogen bis(trifluoromethylsulfonyl) imide (HTf2N), in an experiment to obtain crystals of uranyl bis(trifluoromethylsulfonyl) imide, UO2(Tf2N)(2)center dot xH(2)O. The structure consists of neutral dimers of uranyl (UO22+) units, double bridged by OH- anions. Each uranyl unit is surrounded by one Cl and four O atoms, which form an irregular pentagon, in a plane perpendicular to the linear uranyl groups. The coordination geometry around each U atom can be considered to be distorted pentagonal-bipyramidal. In the crystal structure the uranyl dimers are connected to each other by hydrogen-bonding interactions [O center dot center dot center dot Cl = 3.23 (1) angstrom].