AlN–WC and AlN–Y2O3 composite ceramics were prepared by the resistance-heated hot pressing method at the sintering temperatures of 1873 K and 1973 K. The AlN grains were well-bonded each other by the addition of WC into AlN. W2C-type phase was produced by the addition of WC into AlN ceramics. The bulk density of AlN–WC ceramics was increased with increasing the WC amount, and was in good agreement with the calculated density in ceramics containing 10–50 mol% WC at 1873 K and 1–50 mol% WC at 1973 K. The Young’s modulus for AlN–WC ceramics was increased with increasing the WC amount, reaching for 470 GPa at 50 mol% WC. The addition of WC into AlN ceramics improved mechanical properties, both Vickers hardness and fracture toughness. The AlN–50 mol% WC ceramic had the highest Vickers hardness and fracture toughness value of 17 GPa and 5.9 MPa m0.5, respectively. The thermal conductivity of AlN–WC ceramics was virtually constant at 1–50 mol% WC, ranging between 40 and 60 W m-1 K-1.