Effect of starting granule size and addition of WC on the microstructure and mechanical properties of double Ti(C,N) based cermets was investigated. Results show that the Ti(C,N) based cermets granules distribute in the matrix homogeneously. The amount of hard phases with the white core/grey rim and coreless structures in the matrix increases by increasing WC content. A new phase with the four layer composite structures was also found. With the increase of granules size, the fracture toughness increases, while the transverse rupture strength (TRS) and hardness have an opposite trend. With the increase of WC, the fracture toughness and TRS increase, while the hardness decreases. Higher fracture toughness of double Ti(C,N) based cermets is mainly owing to the branch, bridge and deflection of crack, the formation of micro-cracks at the nearby of the tip of main crack and the pull-out effect of granules.