We have examined to prepare a hybrid thin film consisting of bismuth triiodide and alkylammonium iodide by the conventional spin-coating technique. Their X-ray diffraction profiles and UV-Vis-NIR absorption spectra showed that the two-dimensional (Bi2I93−)xlayer was sandwiched between alkylammonium layers by the molecular fastener effect. The third order nonlinear property of the thin film was estimated by the third harmonic generation (THG) measurements. Strong THG signals were observed from the hybrid thin film with stearylammonium iodide, which gave 10−11esu order of χ(3)values.