Thin films of bismuth titanate Bi4Ti3O12 and different sodium–bismuth–titanate phases Na0.5Bi8.5Ti7O27, Na0.5Bi4.5Ti4O15, and Na0.5Bi0.5TiO3 with different numbers of perovskite units (m) between two Bi2O2 intermediate layers were epitaxially grown on (001) SrTiO3 substrates by metal-organic chemical vapor deposition. The optical properties of these ferroelectric thin films were investigated by spectroscopic ellipsometry (SE) at room temperature in the 0.73–6.48 eV spectral range. In the analysis of the SE measured spectra Cauchy transparent, Tauc–Lorentz and Gaussian dispersion relations were used to characterize the optical properties of the films. Our analysis clearly shows that the refractive index of the Aurivillius phases decreases with increasing m, while the optical band gap increases with increasing m. The obtained dielectric function spectra revealed a shoulder and a broad absorption band at about 3.7 and 4.5 eV, respectively, for Bi4Ti3O12 and a broad absorption band around 4.5 eV for the perovskite phase Na0.5Bi0.5TiO3. A shift in the resonance energies to lower energy with increasing m is observed.