Tungsten inert gas (TIG) welding and laser beam welding (LBW) were employed on as-cast and as-forged Mg−8Li−3Al−2Zn−0.5Y (LAZ832-0.5Y) alloys to investigate their weldability. The microstructure and mechanical properties of solid solution treated samples were investigated for the purpose of further strength improvement, which were treated at 350 °C for 4 h. The ultimate tensile strength (UTS) and yield strength (YS) of the optimal TIG as-cast alloy welding joint were 159 and 122 MPa, which were obtained under the welding current of 80 A, and were lower than the UTS (184 MPa) and YS (146 MPa) of the optimal LBW as-forged welding joint under the power of 2.1 kW/2.0 kW double-side welding. After the solid solution treatment, on the one hand, the growth of α-Mg grains in the fusion zone (FZ), heat affected zone (HAZ) and base metal (BM) of both the TIG and LBW welding joints was insignificant. On the other hand, the larger Al₂Y phases were still present, while the much smaller white AlLi particles were dissolved into the matrix, leading to the solid solution strengthening of the welding joints. As a result, the UTS and YS of the TIG welding joint respectively increased to 216 and 188 MPa after solid solution treatment, and those of the LBW welding joint only increased to 211 and 160 MPa, respectively.