This paper presents a study on graphene-reinforced Al₂O₃-SiCw ceramic composites and the relationship between graphene oxide (GO) loading and the resulting mechanical and electrical properties. Well-dispersed ceramic-GO powders were fabricated using a colloidal processing route. Dense composites were obtained via spark plasma sintering, a technique that has the ability to reduce GO to graphene in situ during the sintering process. The mechanical properties of the sintered composites were investigated. The composite with only a small amount of graphene (0.5 vol.%) showed the highest flexural strength (904 ± 56 MPa), fracture toughness (10.6 ± 0.3 MPa·m^1/2) and hardness (22 ± 0.8 GPa) with an extremely good dispersion of graphene within the ceramic matrix. In addition to these exceptional mechanical properties, the sintered composites also showed high electrical conductivity, which allows the compacts to be machined using electrical discharge machining and thus facilitates the fabrication of ceramic components with sophisticated shapes while reducing machining costs.