Abstract: Transient liquid phase bonding of Tungsten (W) to copper (Cu) alloy using 67Cu-33Mn or 67Cu-33Mn-5Ni (mass fraction) as the interlayer was studied. The microstructures and chemical composition across the bond interface were analyzed by using SEM and EDX. The microstructure of TLP joint using 67Cu-33Mn-5Ni as the interlayer was denser than that of the TLP joint using 67Cu-33Mn as the interlayer. The addition of Ni plays an important role in increasing diffusion rate, isothermally solidification rate and in Ni(W) solid solution formation. The bonding mechanism of W to Cu alloy is found to be a combination of TLP bonding and brazing. The TLP acts as a feasible bonding mechanism of the Cu-Mn interlayer and the Cu alloy, while the brazing mechanism prevails between the interlayer and the W.