We report a reversible thermochromic nanocomposite polymer film composed of fluorescent organogel fibers and a highly cross-linked polymer matrix. A series of cyano-substituted oligo(p-phenylenevinylene) (CN-OPV) derivatives Were synthesized by the reaction of dialdehydes with phenyl or naphthyl acetonitrile under basic conditions. Among the CN-OPV derivatives, NA-DBA having naphtyl moieties and dodecyloxy chains formed a stable organogel in a cross-linkable monomeric solvent (ethylene glycol dimethacrylate). The organogel showed a thenrnoreversible sol gel transition, accompanying the emission color change. A nanocornposite polymer fihn obtained by photopolymerization of the organogel between two quartz plates also exhibited reversible thermochrornism. Under 365 nm irradiation, the orange color of the film at 25 C became yellowish green at 120 C. The fluorescence spectroscopy, DSC, and microscopy results determined that the thermally reversible self assembly of NA-DBA occurred M the polymer matrix, resulting in reversible thermochromism. The melted gelator molecules at 120 C did not diffuse into the polymer matrix probably because of poor interactions of the gelator molecules with the polymer matrix. The NA-DBA molecules dispersed in poly(methyl methacrylate), without forming a supramolecular structure, did not show thennochromism