The 5754 aluminum alloy has been widely used in the automotive industry to reduce the weight of vehicles. The weld-bonding (WB) process comprising resistance spot welding and adhesive bonding processes effectively improves the mechanical properties of joints. However, it is still a great challenge in the WB process to obtain high-quality and defect-free nuggets of aluminum alloys. In this study, the parameters of the WB process are optimized and the mechanism of generation of defects during WB is analyzed. The results show that the welding parameters have a significant effect on the nugget sizes, among which the welding current plays the most important role. The residual adhesive can easily cause defects during welding, e.g., expulsion and porosity in the nugget. This can be effectively avoided by optimizing the welding parameters. In addition, the gas in the joints is effectively reduced by adding an appropriate preheating pulse prior to welding, thus lowering the damage degree of the adhesive layer. As a result, welded joints with better weld nugget quality and more stable mechanical properties are obtained.