This work describes the microstructure, indentation toughness, room and high temperature tribological properties of alumina–carbon nanotubes nanocomposites with various contents of carbon nanotubes prepared by spark plasma sintering. Materials have been studied by SEM, TEM, Vickers indentation technique on the microhardness and nanohardness testers and, by high temperature ball-on-disk tribometer. The microstructure, CNT dispersion, and fracture surface were studied and wearing mechanisms: fiber pull-out, CNT crushing and formation of transferred film were identified. The addition of 5% CNTs increased the indentation toughness from 3.24 MPa m1/2 to 4.14 MPa m1/2. The coefficient of friction of alumina–CNT nanocomposites is approximately three times lower in comparison to the alumina monolithic material due to the lubricating effect of carbon nanotubes during sliding.