The title compound, $(UO_2)_2Cl_2(OH)_2(H_2O)_4$, was obtained unintentionally as the product of an attempted reaction between uranium(VI) oxide dihydrate, $UO_3·2H_2O$, and hydrogen bis(trifluoromethylsulfonyl)imide $(HTf_2N)$, in an experiment to obtain crystals of uranyl bis(trifluoromethylsulfonyl)imide,$UO_2(Tf_2N)_2·xH_2O$. The structure consists of neutral dimers of uranyl $(UO_2^{2+})$ 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 $[O\cdotsCl$ = 3.23 (1) Å].