Porous SiC ceramics were fabricated by the carbothermal reduction of polysiloxane-derived SiOC containing hollow microspheres followed by sintering. The effect of the Al₂O₃–Y₂O₃–CaO (AYC) content on the microstructure and flexural strength of the porous SiC ceramics were investigated. The growth of large platelet α-SiC grains increased with increasing additive content due to enhanced grain growth and the β → α phase transformation of SiC. In situ toughened microstructures consisting of large platelet grains and fine equiaxed grains were obtained when 10 or 20 wt% AYC was added. The porosity generally decreased with increasing the additive content, whereas the flexural strength increased. The typical flexural strength of the porous SiC ceramics sintered with 10 wt% AYC was 61 MPa at a porosity of 44%.