<p>This study systematically investigates the influence of laser welding parameters (welding speed, defocusing amount, and shielding gas flow rate) on the morphology, microstructure, hardness, and tensile properties of laser-welded die-cast A356 aluminum alloy joints. The results reveal that lower welding speeds and smaller defocusing amount increase heat input, resulting in wider welds and larger fusion zones (FZ). In contrast, higher welding speeds promote gas escape from the molten pool, thereby effectively reducing porosity. Microstructural characterization indicates that, with increasing welding speed, the proportion of equiaxed grains decreases, while columnar grains become more dominant. Grain size and grain boundary orientation are also influenced by defocusing amount and welding speed. The heat-affected zone (HAZ) exhibits the lowest hardness, whereas the FZ hardness increases with higher welding speeds and reaches a maximum at a defocusing amount of 0&#xa0;mm. Tensile testing demonstrates that both ultimate tensile strength (UTS) and yield strength (YS) of the welded joints exceed those of the base metal (BM). Compared with FSW joints, LBW joints exhibit lower elongation yet superior YS and UTS. Fracture predominantly occurs in the BM or HAZ under optimal process parameters. Shielding gas flow rate significantly affects porosity formation, thereby influencing joint fracture location.</p>