A method using a thin film/diffusion barrier/substrate trilayer structure approach is presented to determine the biaxial moduli and thermal expansion coefficients of gold (Au) thin films using a bending beam technique. Silicon and gallium-arsenide substrates were used. A thin layer of tungsten was deposited on the substrates as a diffusion barrier prior to the deposition of Au thin films. The measured thermal expansion coefficients of the thermally evaporated Au thin film ranges from 13.9 to 14.8 p.p.m. degrees-C-1, while that of bulk gold is 14.2 p.p.m. degrees-C-1. Also, the measured biaxial modulus is similar to that of bulk gold, but it obviously decreases upon annealing.