A pi-conjugated coordination nanosheet (CONASH) comprising bis(iminothiolato)nickel moieties, NiIT, was synthesized by a reaction of Ni2+ with 1,3,5-triaminobenzene-2,4,6-trithiol (L) in the presence of ferrocenium ions. A bulk material, bulk-NiIT, prepared in a homogeneous solution was characterized by XPS, IR, and SEM. A liquid-liquid interfacial reaction using bis(2,4-pentanedionato) nickel(II) in CH2Cl2 and L in H2O afforded a semiconducting nanosheet, nano-NiIT. AFM, SEM, and TEM observation of nano-NiIT revealed the uniform and flat nature of a stacked layer nanosheet. Selected-area electron diffraction (SAED) analysis indicated the formation of a two-dimensional hexagonal crystal structure.