Aluminum alloy is the most widely used light alloy at present. By combining different types of aluminum alloys, their functional properties can be expanded. In the present research, two components composed of 2319 (Al-6.5Cu) and 5B06 (Al-6.4Mg) dissimilar alloys were fabricated by wire and arc additive manufacturing (WAAM). The deposited component with the bottom half of 2319 and the top half of 5B06 exhibits better mechanical properties than its counterpart deposited vice versa. Its ultimate tensile strength, yield strength, and elongation are 258.5 MPa, 139.3 MPa, and 5.6%, respectively, which are only slightly inferior to the mechanical properties of 2319 base metal. The results show that for both components, fracture occurred at a layer thickness above the interface layer during the tensile test, regardless of the deposition order. It appears that the thermal stress due to the long dwell time and the remelting of the S-Al₂CuMg phase are the main factors promoting crack initiation. Depending on the deposition order, cracks propagate either along the aggregated pores or strip θ-Al₂Cu phase distributed along the grain boundary. By analyzing the heat input and selecting the appropriate depositing order, the strength of WAAM dissimilar aluminum alloys can be effectively improved through the proper control of microstructure and internal defects.