Ceramic materials exhibit very low fracture toughness, which limits their applications. Recently, metal-ceramic composites have been developed to achieve improvements in toughness. In this work, the fracture toughness of SiC-Cu based alloys cermets, obtained by reactive infiltration, was measured at room temperature using the single edge notched beam (SENB) method. Values up to I I MPam(1/2) were obtained; these values were compared with the fracture toughness of commercial materials. The results of fracture toughness were directly related with the amount of the infiltrated metallic phase. The fracture energy was calculated using values of K-IC and Young Modulus obtained from four points bending tests. Differences on toughness values were related with porosity and type of fracture of the several systems. The microstructural analysis of the fracture surfaces was carried out by scanning electron microscopy. The role of different operating toughening mechanisms; such as crack deflection, bridging, branching, and energy dissipation through microcracking and/or microplasticity; has been examined.