<p>Resistance spot welding (RSW) is a widely used welding process in the automotive, rail, aerospace, and electrical industries. In the current research, a modified version of the RSW process called ultrasonic-assisted RSW was used to join aluminium alloy 5754 and titanium alloy grade 2. The joining specimens were vibrated by the ultrasound in the whole welding process, which is transferred by the lower electrode. The ultrasonic generator has a power of 800 W. The characteristics of the joint, such as its microstructure and mechanical properties, were studied. The findings indicate that the weld interface of the spot-welded joint produced by the non-ultrasound-assisted RSW exhibits a discontinuity, with the presence of cracks along the weld interface. In contrast, the weld interface of ultrasonic-assisted welding displays continuity, albeit with a shorter length. However, the tensile shear test results show that the welded joint of the ultrasonic-assisted RSW process has superior mechanical properties, as measured by maximum displacement, peak load and failure energy. The study demonstrated that the application of ultrasonic vibration exerts a distinct influence on the welding process.&#xa0;</p>