Using Ni-Ti duplex foils as joining materials, Ti₃Al alloy was bonded to Ti₂AlNb alloy by transient liquid phase (TLP) diffusion bonding at 990 °C under low bonding pressure (0.1 MPa). The effects of bonding time on the microstructure and mechanical properties of Ti₃Al/Ti₂AlNb joint were analyzed, as well as the interfacial evolution and forming mechanism of the TLP joint were studied. Results show that the Ti₃Al/Ti₂AlNb alloy joints with typical interface structure of Ti₃Al | Al_0.5Nb_0.5Ti₃ | residual Ni | NiTi | NiTi₂ | residual Ti | Al_0.5Nb_0.5Ti₃ | Ti₂AlNb can be formed. In addition, with the extension of bonding time, the shear strength of the joint first increases and then decreases, and the maximum shear strength, up to 167±12 MPa, of the Ti₃Al/Ti₂AlNb alloy joint can be achieved when the bonding time reaches 60 min. The joint fracture, characterized by brittle fracture, mainly occurs at the NiTi₂ layer adjacent to the Ti₂AlNb/Ti interlayer and extends to the Ti interlayer.