The design of new composite ceramic materials based on zirconium carbide is one of the effective methods of controlling the inherent brittleness of materials. A key physical parameter characterizing the ability of a material to resist crack growth is fracture toughness. A numerical method for estimating this parameter for heteromodulus ZrC ceramic materials under uniaxial compression is presented. It is shown that an introduction of low-modulus (in comparison with the matrix) particles delays the fracture and reduces the integral brittleness of the material due to the implementation of additional fracture mechanisms. It is demonstrated that, based on the mechanical response of the mesovolume of the material with an explicit consideration of the microstructure under uniaxial compression, it is possible to estimate the fracture toughness in a satisfactory agreement with the experimental data