As one of most broadly utilized structural ceramics, Al2O3 has been studied intensively because of its remarkable room-temperature mechanical properties. The potential applications of Al2O3 are limited at elevated temperatures due to grain-boundary sliding, grain rotation and diffusional creep. However, Al2O3-based eutectic ceramic composites have been shown to effectively suppress high temperature deformation mechanisms during the last decade. These eutectic ceramics have exceptional strength and high temperature creep resistance. Among these rare-earth aluminates, SmAlO3(SAP) has attracted attention because of its excellent microwave dielectric, magnetic, and electrical properties. Here, a modified microcantilever bending test is employed to investigate the fracture toughness and crack propagation in these composites at the single grain level. The results suggest that the fracture properties of Al2O3-SAP ceramics strongly depend on the interface strength/toughness, component phase strength/toughness, and geometry. Finite element method (FEM) analysis is used to simulate microstructural effects and the calculate the fracture toughness Keff.