The effect of multi-walled carbon nanotubes (MWCNTs) and hexagonal boron nitride (h-BN) inclusions on the fracture toughness of yttria-stabilized zirconia (YSZ) ceramics has been studied. It is shown that an increase in the MWCNTs and h-BN content has a positive effect on the K1C of zirconia ceramics. The greatest increase in the fracture toughness of YSZ ceramics was observed with the introduction of hexagonal boron nitride particles. For YSZ ceramics, the K1C value was ≈6.1 MPa m1/2, for ceramics with a 5 wt % of h-BN K1C ≈ 9.2 MPa m1/2. It was shown that an increase of the YSZ ceramics fracture toughness with the introduction of MWCNTs and h-BN, both and separately was provided by the combined action of several mechanisms of increasing the work of crack propagation. In addition, in all composites obtained in this work, the transformation of tetragonal ZrO2 into monoclinic was observed.