An optimum route to fabricate the Al2O3/Cu nanocomposites with sound microstructure and improved mechanical properties was investigated. Three powder mixtures of Al2O3 and Cu, CuO or Cu-nitrate were used to obtain Al2O3/5 vol% Cu composites. Microstructural investigations for the composite from Al2O3/Cu-nitrate showed that fine Cu particles, about 150 nm in diameter, were homogeneously distributed within the Al2O3 matrix grains and at the grain boundaries. Fracture toughness of 4.8 MPam and strength of 953 MPa were measured for the Al2O3/5 vol% Cu nanocomposites prepared from Al2O3/Cu-nitrate mixture. The toughening and strengthening of the composites are explained by the crack bridging/deflection and the refinement of the microstructure, respectively.