A novel high-nuclear nanosized cluster modified by conjugated organic ligands (pyridine and imidazole), [C5NH5]8[C3H5N2]2{[C5NH5]9[H31Mo12O24Co12(PO4)23(H2O)4]}·12H2O (1), has been successfully isolated under hydrothermal conditions and structurally characterized. Compound 1 consists of 12 CoII and 12 MoV ions linked by 23 {PO4} groups, exhibiting unprecedented nanosized ship-shaped clusters. The magnetic measurements reveal that compound 1 exhibits dominant antiferromagnetic interactions. Additionally, pyridine and imidazole ligands enhance the delocalized electron effects of clusters, and the third-order nonlinear-optical response of compound 1 is excellent.