A novel bis-diol monomer, 3,3'-bis-(2-hydroxyethyl)-2,2'-dithioxo-[5,5']bithiazolidinylidene-4,4'-dione, was prepared in a one-pot three component reaction and used in a polyesterification reaction with various aromatic dicarboxylic acids using tosyl chloride/dimethylformamide/pyridine system as a condensing agent in order to generate a series of new polyesters. The prepared polyesters were characterized by FTIR spectroscopy and elemental analysis. In the next part, a series of polyester/clay nanocomposites were synthesized through a polyesterification reaction of the synthesized monomer with iso-phthalic acid. Cloisite 30B was used as the filler at different concentrations. Wide-angle X-ray diffraction and transmission electron microscopy studies showed that the organoclay layers are mainly exfoliated in the nanocomposites containing 1 wt % of Cloisite 30B.