The effect of the thickness on the dielectric and ferroelectric properties of poly(vinylidene fluoride trifluoroethylene) [P(VDF-TrFE)] copolymer thin films were investigated. The results show that the dielectric constant and tunability increase while the coercive field decreases with increasing film thickness. The film thickness also affects both the reversible and irreversible Raleigh parameters in the ac field dependence of dielectric constant. The observed phenomenon can be explained by the existence of interfacial layers between electrodes and film. No obvious thickness-dependent microstructure and ferroelectric transition temperature was observed.