The anisotropic properties of polyethylene terephthalate film resulting from its manufacturing process are quantitatively investigated in terms of its optical, mechanical, and photoelastic aspects. Transmission ellipsometers and a Jones-matrix-based analysis software together with a 4 × 4 Berreman-matrix-based analysis software are adopted to determine the wavelengthdependent in-plane birefringence, the principal refractive indices, and the orientation of the optical axis. Mechanical anisotropy is characterized in terms of the elastic compliance tensor components using the measured azimuthal angle-dependent Young's modulus and Poisson's ratio. From the measured variation of the wavelength-dependent in-plane birefringence as a function of tensile stress, the dispersive photoelastic coefficients are obtained for a few sample azimuthal angles, and the components of the photoelastic tensor are determined.