<p>Mullite fiber aerogels are suitable for high-temperature insulation and other extreme environment applications due to their low density, excellent thermal stability, and low thermal conductivity. However, the elevated thermal conductivity at high temperatures and the limited mechanical strength confined its wider application. In this paper, mullite fibers/silicon carbide (SiC) composite aerogels were prepared by freeze-drying method with polycarbosilane (PCS) as a precursor. The SiC formed during the pyrolysis of PCS served as a high-temperature binder, which can form a tough three-dimensional network structure with mullite fibers. Benefit from the good infrared shielding property and high strength of SiC phase, the high-temperature insulation and mechanical properties of the aerogels were greatly improved. The lowest thermal conductivity of the mullite fibers/SiC aerogel can be 0.037 W·m⁻¹·K⁻¹ at room temperature and 0.067 W·m⁻¹·K⁻¹ at 1000 °C. Meanwhile the compressive strength can reach 0.31 MPa (10% strain). These favorable properties make it a very promising material in high temperature insulation applications.</p> Graphical Abstract <p></p>