An organic–inorganic coplanar-shaped hexa-CuII sandwiched hybrid, (H2en){[Cu(en)2]2[Cu2(en)2Cu4(H2O)2](B-α-AsW9O34)2} · 5H2O (en = ethylenediamine) (1), has been synthesized via hydrothermal method and further characterized by IR spectroscopy, thermogravimetric analysis, and X-ray single-crystal diffraction. Single-crystal X-ray diffraction analysis shows that 1 contains an organic–inorganic hybrid polyoxoanion {Cu2(en)2Cu4(H2O)2(B-α-AsW9O34)2}6−, which can be described as a coplanar-shaped hexa-CuII cluster sandwiched by two trivacant [B-α-AsW9O34]9− fragments. Complex 1 represents a rare organic–inorganic coplanar-shaped hexa-CuII cluster sandwiched arsenotungstate. Magnetic susceptibility measurements indicate that 1 demonstrates ferromagnetic coupling interactions within the CuII centers.