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Alloying Ti–Al–N coatings with Ta has proven to enhance their hardness, thermal stability, and oxidation resistance. However, especially for arc-evaporated Ti–Al–Ta–N coatings only limited information on the detailed influence of the elements on various properties is available. Therefore, we have developed arc-evaporated Ti_1−x−yAl_xTa_yN coatings with various Al (x = 0.50–0.65) and Ta (y = 0.00–0.15) contents. While the thermal stability of our coatings during annealing in inert He atmosphere increases with increasing Ta content, best results are obtained for specific Ta–Al ratios during oxidation. Single phase cubic Ti_0.32Al_0.60Ta_0.08N yields a mass-gain of only ~ 5% after 5 h at 950 °C in synthetic air, whereas Ti_0.35Al_0.65N is completely oxidized after 15 min. This is in part based on the suppressed anatase and direct rutile TiO₂ formation at a defined Ta–Al content. Consequently, the anatase-to-rutile …