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Continuous silicon carbide fiber reinforced silicon carbide matrix composites (SiC f /SiC) are promising candidate materials for nuclear applications. In this paper, three–dimensional (3D) SiC f /SiC composites were fabricated using the polymer infiltration and pyrolysis (PIP) process at different pyrolysis temperatures (i.e. 1100, 1300 and 1500 °C). The effect of the pyrolysis temperature on the thermal and mechanical properties of the SiC f /SiC composites was investigated with a laser flash method, a three–point bending test and a single–edged notch beam method. The results indicated that the thermal diffusivity of the SiC f /SiC composites improved considerably with increasing pyrolysis temperatures, due to a higher degree of crystallization in the matrix. Additionally, as the testing temperature increased, the thermal diffusivity of the SiC f /SiC composites gradually decreased. With increasing pyrolysis temperatures, the mechanical properties of the SiC f /SiC composites first increased and later decreased. The SiC f /SiC composites fabricated at 1300 °C had the highest average flexural strength and fracture toughness, i.e. 535.6 MPa and 17.3 MPa m 1/2 , respectively. [ABSTRACT FROM AUTHOR]