A novel type of all-ceramic SiC aerogel was fabricated by freeze casting and carbothermal reduction reaction processes using graphene oxide (GO) doped SiC nanowires suspensions as starting materials. The effect of GO addition (0, 1, 2, and 4 mg/mL) on the porous morphologies, chemical composition, and the electromagnetic (EM) performance of the SiC aerogels were investigated. The optimum all-ceramic SiC aerogel exhibits effective whole X-band attenuation (>90%) at a fixed thickness of 3.3 mm from room temperature to 400 °C. It is ultralight with a density of 0.2 g/cm 3 and possesses a low thermal conductivity of about 0.05 W/mK. The material composition remains stable at temperatures up to 800 °C. The lightweight, high thermal stability, low thermal conductivity, and excellent X-band attenuation performance at a fixed thin thickness make the all-ceramic SiC aerogels potential EM attenuation materials for many applications in harsh environments.