Thin, silicon‐rich tungsten silicide layers, deposited using the co‐sputtering technique and annealed within the temperature range 750–950 °C, were investigated using the acoustic material signature technique, transmission electron microscopy, and the Rutherford backscattering technique. The effective elastic constants were determined from the dispersion curves calculated using a Tiersten model [J. Appl. Phys.40, 2 (1969)] and fitted to the experimental dispersion data. It is shown that for the annealing temperatures used the elastic properties of thin silicide films are correlated with the annealing temperature‐dependent content of the excess silicon present within the grain boundaries.