Thin films of tin phthalocyanine were prepared on quartz substrates by thermal evaporation technique. The optical properties were investigated using a spectrophotometric measurement of transmittance and reflectance at normal incidence of light in the wavelength range 200-2500 nm for the as-deposited and the annealed films. Absorption spectra of the films show intense B, N and C bands in the UV region followed by Q-band in the visible region. The values of the oscillator strength and the electric dipole strength were estimated. The optical constants were accurately determined using Murmann's equations, which allow obtaining the real and the imaginary parts of the complex refractive index. The absorption analysis has been also performed to determine the type of electronic transition and the optical energy band gap. The dispersion of the refractive index, n, is discussed in terms of the single oscillator model. The dispersion parameters and the ratio of free carrier concentration to the free carrier effective mass were also estimated. (C) 2008 Elsevier B. V. All rights reserved.