Polyester foils were used as substrate material for zinc sulfide thin films grown by the successive ionic layer adsorption and reaction method. The polyester substrates were pretreated with 0.1 M SnCl2 to attain a good adhesion between zinc sulfide and the substrate surface. The growth rate of the ZnS thin film was 0.16 nm/cycle when precursor solutions of 0.1 M ZnCl2 and 0.05 M Na2S were used, and 0.22 nm/cycle when the concentrations of the precursor solutions were doubled. Thin ZnS films grown On polyester were amorphous, but when the film thickness exceeded 250 nm, the films showed crystallinity on X-ray diffraction. The films were slightly zinc rich and contained some oxygen, possibly as zinc oxide and water. The band gap of the ZnS thin films was 3.44 eV. The films appeared to be smooth and homogenous and the attachment of the ZnS thin film to the polyester substrate was good.