The mechanism of high-temperature creep deformation during compression tests of ceramic tungsten carbide samples with different particle size has been studied. Tungsten carbide samples with high relative density (96.1–99.2%) were fabricated by the method of high-speed spark plasma sintering (SPS) from nano-, submicron, and micron powders of α-WC. Creep tests were carried out in two modes: isothermal holding at different temperatures (1300–1375°C) at a specified compression, which enabled one to evaluate the creep activation energy, and tests by the method of “compression jumps” at a temperature of 1325°C, which enabled one to estimate the value of the coefficient n in the equation of power creep. It was shown that the creep activation energy in ultrafine-grained (UFG) tungsten carbide with a grain size of ~0.15 μm sintered from plasma chemical nanopowders was ~31 kT m . This value was 1.5–2 times higher that the creep activation energy in fine-grained tungsten carbide samples produced by the SPS method from submicron (~0.8 μm) and micron (~3 μm) industrial powders. It was determined that the value of the coefficient n varied from 2.4 to 3.1, which corresponds to the case of the movement of lattice dislocations in the field of uniformly spaced point obstacles. It was assumed that one of the reasons for the increase of the creep activation energy during testing of UFG tungsten carbide samples was the increased volume fraction of particles of lower carbide W 2 C formed during high-speed sintering of plasma chemical nanopowders α-WC with an increased concentration of adsorbed oxygen.