A new lithium copper diselenite chloride hydrate, Li₂Se₂O₅(H₂O)_1.5·CuCl₂, was prepared from aqueous solution. Its unique 2D structure can be interpreted as Li₂Se₂O₅(H₂O)_1.5layers with CuCl₂hosts embedded in the interlayer space, and be considered halfway between the salt-inclusion and host-guest structures. The CuO₂Cl₄octahedra form chains similar to those in CuCl₂·2H₂O, yet water molecules are coordinated exclusively to Li⁺while Se₂O₅²⁻and Cl⁻bridge Li⁺and Cu²⁺. The complexity of the structure is likely responsible for both very long pre-crystallization time and non-existence of the corresponding bromide analogue. Despite the relatively long Cu⋯Cu separations, the compound exhibits weak ferromagnetic interactions along the chains of CuO₂Cl₄octahedra.