The microstructure, mechanical properties, fracture behaviour and toughening mechanisms of Al2O-20 vol % ZrO2 (2 mol % Y2O3)-20 vol% SiCW ceramic matrix composite were investigated by X-ray diffraction, scanning and transmission electron microscopies, energy dispersive analysis of X-rays, high-resolution electron microscopy techniques and three-point bending tests. The results-show that-the Al2O3 matrix is simultaneously strengthened and toughened by both ZrO2 particles and SIC whiskers. The interfacial amorphous layers between SIC whiskers and ZrO2, and Al2O3 grains were observed by both TEM dark-field and high-resolution electron microscopy techniques.