Air-methane and nitrogen-hydrogen DC thermal plasma confined flows were used to synthesize tungsten carbide and vanadium carbide nanopowders. The influence of input process parameters such as C/W and C/V molar ratio, plasma jet chemical composition, plasma jet enthalpy, and reactants flow rates on the average nanoparticle size, chemical and crystallographic phase compositions were investigated. During post heat treatment, the synthesized MeC1-x nanopowders were fully carburized to monocarbides WC and VC with particles size less than 80 and 40 nm correspondently.