In the present study, the oxidation behavior of WC-12Co prepared by mechanical milling and spark plasma sintering was investigated in dry air (DA) and water vapor (WV) atmospheres at 400–800 °C. The results indicated that the oxidation rate increased significantly with increasing temperature, and the oxidation was significantly accelerated in water vapor compared to dry air. The Vickers hardness decreased after high-temperature exposure, which was influenced by the alterations in structural integrity observed in the material. The formation of Co3O4, WO3, and CoWO4 oxides was observed with distinct morphological changes at elevated temperatures. As the temperature increased, the oxide layer became thicker and more porous, with the appearance of cracks. Enhanced porosity facilitated pore link formation, serving as diffusion pathways for oxygen, water vapor, and metal ions. Notably, oxidation in a water vapor atmosphere resulted in a thicker and more porous oxide layer compared to that in dry air, driven by the release of additional H2 gas alongside CO2/CO and other volatile species. This study provides valuable insights into the oxidation mechanisms of WC-12Co at high-temperatures, offering critical implications for its application in cutting tools and wear-resistant components. © 2026 Elsevier Ltd