SiC-platelet reinforced Al2O3/SiC-particle nanocomposites were fabricated by hot-pressing the mixture through the conventional powder mixing process. The mechanical properties of Al2O3/SiC-particle/SiC-platelet hybrid composites were evaluated. Fracture toughness and work of fracture were increased by the incorporation of SiC-platelets into Al2O3/SiC-particle nanocomposites. The typical rising R-curve was shown during crack growth for these hybrid nanocomposites, whereas Al2O3/SiC-particle nanocomposites showed the constant K-R value and no rising R-curve. The further improvement of Al2O3/SiC-particle nanocomposites in the creep resistance was observed by the addition of SiC platelets. The relationship between the microstructure and mechanical properties for Al2O3/SiC-particle/SiC-platelet hybrid composites was discussed.