The structure of poly[[(ethylenediamine-kappa2N,N')cobalt(II)]-mu-tetraoxomolybdato(VI)], [Co(C(2)H(8)N(2))MoO(4)](n) or [CoMoO(4)(C(2)H(8)N(2))](n), is composed of puckered layers constructed from MoO(4) tetrahedra and CoN(2)O(4) octahedra, with the ethylenediamine ligand coordinated to the Co atom in a cis fashion. Each pair of cobalt sites forms a binuclear edge-sharing unit through a (Co(2)O(2)) interaction. The binuclear octahedral units are interconnected through the bridging MoO(4) tetrahedra into a layer structure.