Submicron powder of non-stoichiometric hafnium carbonitrides (HC0.5N0.2) was fabricated by the mechanochemical synthesis method. It was shown that during the first milling stages, primarily reaction between hafnium and carbon took place. The nitridation occurred later when fresh metal surfaces started to form through defragmentation of the brittle layer of a carbon-solid solution. The synthesized powder was consolidated by spark plasma sintering approach to producing dense bulk hafnium carbonitride ceramics. Hardness and fracture toughness measured on consolidated samples were 20.8 +/- 1 GPa b 3.5 +/- 0.2 MPa.m(1/2), respectively. The obtained results were compared with previously reported data. (c) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.