Abstract: To address challenges of reduced dimensional accuracy and low-quality output due to excessive interlayer heat buildup in wire arc additive manufacturing of aluminium alloys, the effect of varying interlayer waiting times (0, 15, 30, 45 s) on the microstructures and mechanical properties of 5356 aluminium alloy wire arc additive manufacturing was studied. The dimensional characteristics of the multilayer single-channel straight wall specimens with different waiting time between layers were analyzed, and the mechanical properties such as microstructure analysis, microhardness and tensile properties were tested. Findings indicate that interlayer waiting time significantly impacts the macroscopic morphology of straight-walled specimens produced via wire arc additive manufacturing using 5356 aluminium alloy. When the waiting time between layers gradually increases from 0 s to 45 s, the width of the straight-wall specimens decreases by 1.65 mm and the height of the single-layer specimens increases by 0.37 mm. The microstructure primarily is mainly composed of α-Al matrix and β-Al₃Mg₂ phase, and with the increase of interlayer waiting time, the coarse β microstructure decreases in size and increases in density. As interlayer waiting time increased, tensile strength and elongation rose in both horizontal and vertical specimens, with horizontally oriented specimens displaying marginally higher values than vertically oriented ones. Numerous tough nests appeared within the fracture zones of tensile specimens under varying interlayer waiting times. As waiting time increased, the tough nests enlarged, became more uniformly distributed, and plastic deformation capacity was enhanced. This study can provide a theoretical basis for advancing wire arc additive manufacturing applications of 5356 aluminium alloy.