Si₃N₄ ceramics with improved and tailorable dielectric constant are desirable for microwave dielectric substrate application in harsh environment. Effect of BaTiO₃ addition on the mechanical and dielectric properties of the hot-pressed Si₃N₄ ceramics with Al₂O₃ and Nd₂O₃ as sintering additives were investigated. Relative density, flexural strength and Vickers’ hardness of Si₃N₄ ceramics all decreased, while indentation fracture toughness increased monotonically with the increase of BaTiO₃ content. Flexural strength of Si₃N₄ ceramics was higher than 600 MPa and dielectric constant of Si₃N₄ ceramics increased to 9.26-11.50 when 5wt%-20wt% of BaTiO₃ was added. The dielectric loss was at the level of 10^-3. The improvement of dielectric constant was attributed to the formation of TiN during hot pressing, as crystalline BaTiO₃ was not detected in the sintered samples. These findings can make a significant contribution to the new applications of Si₃N₄ ceramics.