The oxidation kinetics of reactively sputtered amorphous Ta36Si14N50thin films are studied in dry and wet ambient in the temperature range of 650–850 °C by backscattering spectrometry, Dektak profilometer, and x‐ray diffraction analyses. The dry oxidation is well described by a parabolic time dependence which corresponds to a process controlled by the diffusion of the oxidant in the oxide. The growth of the oxide in wet ambient is initially very rapid and then proceeds linearly which means that the process is reaction limited. Both oxidation rates are thermally activated. The activation energies are 2.0 eV for dry and 1.4 eV for wet ambient. The pre‐exponential factors are 0.17×1016A˚2/min and 7.4×108A˚/min, respectively. Both the dry and wet oxidation of the amorphous ternary Ta36Si14N50film result in the formation of an x‐ray amorphous Ta14Si5.5O80layer.