We report the use of organic additive carbazole as a structural modifier to change the mesophase of the mesostructured silicate cetyl trimethyl ammonium bromide (CTAB)-templated sol-gel thin films. The films were made by a dip-coating method on glass slides, which results in optical transparency. The films were characterized by X-ray diffraction patterns. For the small molar concentrations of carbazole (0.1-0.41) to CTAB, the films exhibit a two-dimensional hexagonal structure, which is also obtained for the films that do not have carbazole. As the molar concentration increases from 0.43 to 1.2, surprisingly the films acquire a lamellar structure with an extremely long-range order. This is an unusual result for the films prepared with CTAB, which always gives a hexagonal structure. We study the solvent effect to understand the cause of such a dramatic transformation in the films.