A major challenge in the development of high-efficiency high-temperature solar receivers for concentrated solar power plants is the development of high-temperature materials with an ideal spectral selectivity (high solar absorptivity and low hemispherical total emissivity). TaC could be an interesting candidate due to its very good spectral selectivity, which could be increased by surface treatments and microstructuring. However, Ta2O5 presents the opposite selectivity. Therefore, we investigated the oxidation of TaC in air and in helium at 1100 K and determined the impact of this oxidation on the optical and thermal properties using reflectivity and bidirectional reflectance distribution function (BRDF) measurements and laser flash analysis (LFA), respectively. We observed that the oxidation in air was too severe. Additionally, the samples treated in helium were sufficiently oxidized by the residual oxygen to lose their spectral selectivity. Therefore, despite its promising optical properties, TaC cannot be used for high-temperature applications in air or even in helium.