Spark plasma sintering (SPS) technology has been employed to obtain nanocomposites of a silicon oxycarbide glass matrix (SiOC) reinforced with SiC, SiO 2 or Al 2 O 3 nanoparticles. The characterization of the obtained materials revealed a dependence on the structural characteristics of the precursors with the properties and the reactions taking place during sintering. In the materials reinforced with SiO 2 , the stoichiometry of the oxycarbide phase is independent on the carbon content in the SiOC whereas when reinforcing with Al 2 O 3 , the mullite phase formation occurs at expense of the SiOC metastable phase. The measured mechanical and electrical properties have been revealed to be dependent of the size of the carbon nanodomains.