We measured the coefficient of linear thermal expansion of ZnSe thin films with a temperature regulated spectroscopic ellipsometer. The change in the film thickness was found to be a quadratic function of temperature whereas the coefficient of linear thermal expansion varied linearly in the temperature range between 295 and 413 K. Tt While spectroscopic ellipsometry is recognized as a measurement technique to determine thin film optical constants and him thickness, the present work expands upon this technique to measure temperature induced dimensional change in the Angstrom range.