<p>The development of reliable polymer–metal hybrid joints is essential for lightweight structural applications in automotive, aerospace, and electronics industries. This work investigates the dissimilar joining of AA6061 aluminium alloy with two types of thermoplastics, PMMA and PC, using a novel ultrasonic-assisted induction welding process. The study focuses on the influence of ultrasonic vibration on the joint interface characteristics, bubble formation, and mechanical performance compared to conventional static loading during induction welding. Aluminium surfaces were subjected to various surface modifications (through-hole and grooves) and combined chemical (NaOH) pretreatment. Characterisation of hybrid joints includes shear tensile testing, scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) analysis. The results showed that the use of ultrasonic vibrations significantly reduces the formation of bubbles. The high-frequency vibrations enhance the flow of the molten polymer and promote the escape of entrapped gases, leading to a defect-free joint interface. The joints made with ultrasonic-assisted loading exhibited higher fracture loads compared to their static counterparts, particularly when combined with surface modification and chemical treatment of AA6061. Maximum shear strengths of 6.3 and 3.8&#xa0;MPa were achieved for the PC/AA6061 and PMMA/AA6061, respectively.</p>