Thixo-joining as a method of joining dissimilar materials was introduced recently. In this method, specimens in a semi-solid condition are brought into contact with each other under compression. As a result, diffusion bonding takes place between the specimens. In this research, two kinds of tool steels, AISI D2 and AISI M2, which are difficult to join using conventional methods, were joined together through the thixo-joining process. While specimens were being heated in a furnace with argon-controlled atmosphere through the direct partial remelting method, a uniaxial constant compressive load was applied to them. The Microstructure and mechanical properties of the joint were analyzed using scanning electron microscopy, shear, and hardness tests. The results showed a joint with good quality regarding the microstructure and mechanical properties. Moreover, energy dispersive spectroscopy revealed the diffusion of elements during the joining process. The fracture surface of the joint was also analyzed and characterized as intergranular.