Abstract Nearly fully dense ZrB2–SiC–graphite composites were fabricated from commercially available powder at 1900°C by hot pressing. The tensile strength of ZrB2-based ceramics was measured in air up to 1750°C, which is the first reported tensile strength measurement in air above 1500°C. A mechanical testing apparatus capable of testing material in ultra-high temperature under air atmosphere was built, evaluated, and used. Tensile strength was measured as a function of temperature up to 1750°C in air. The respective average values of the tensile strength measured at 1550°C, 1650°C, and 1750°C are 58.4, 44.8, and 21.8MPa, which are 49.4%, 37.9%, and 18.4% of their room-temperature strength (118.2MPa), respectively. Moreover, the tensile fracture behaviors and mechanism of ZrB2-based ceramics at different testing temperatures were discussed based on microstructure characterization.