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Three-dimensional (3D) needled C/SiC composites were prepared and subjected to three-point bending tests from room temperature (RT) to 2000 ℃ under vacuum. The results show that the flexural strength and modulus increase in the range of RT to 800 °C due to the release of thermal residual stress (TRS). At 800–1700 °C, the modulus further increases for the further release of TRS, while the destruction of the pyrolytic carbon (PyC) coating reduces the flexural strength. Up to 2000 ℃, the thermal mismatch stress in the composites cause fiber slippage and matrix crack deflection to be zigzag, which increase the fracture strength. The change of components properties mediated by high temperature and the release of TRS play a leading role in the flexural strength and fracture mode. The results provide important support for the mechanical behavior of 3D needled C/SiC composites at ultra-high temperature. • 3D needled C/SiC composites were prepared by CVI-GSI method and subjected to bending tests up to 2000 ℃ under vacuum. • Mechanical behavior and the microcosmic failure mechanism of 3D needled C/SiC composites at high temperature are presented. • The change of properties of 3D needled C/SiC composites after high temperature treatment was analyzed. [ABSTRACT FROM AUTHOR]