Thermophysical properties of ZrCxNy ceramics prepared from powders produced via a two-step carbothermic reduction-nitridation of zirconia were characterised to 2200 K. Preliminary evidence for the mechanism of nitridation shows a gas-solid phase reaction at the ZrC particle surface which is the first such observation with this system. Electrical and thermal conductivities were higher than commercially available ZrC and ZrN. Thermal conductivity values of the ZrCxNy phases at room temperature were between 35 and 43 Wm-1 K-1, increasing with nitrogen content due to increased electronic contribution to thermal conduction and increased to 40-50 Wm-1 K-1 with temperature. Electrical conductivity also increased with nitrogen content and values were in the range of 100-450 × 104Ω-1 m1, but decreased with increasing temperature showing metallic behaviour. © 2014 Elsevier B.V. All rights reserved.