Lightweight materials such as aluminium and thermoplastics have gained increasing popularity in various manufacturing industries because of their advantageous characteristics, including high strength-to-weight ratios, corrosion resistance, and self-insulating properties. In recent years, friction stir welding has emerged as a solid-state joining process that is well-suited for joining thermoplastics and aluminium. This is in contrast to fusion heat-assisted welding methods, which may not be suitable for lightweight materials due to their unfavourable thermal properties. Friction stir welding is a solid-state process that does not rely on melting the materials. In the present study, we explore the possibility of using FSW to join dissimilar materials, specifically polycarbonate (PC) and aluminium alloy Al6061. The thermoplastic polycarbonate is overlaid onto the metallic aluminium (Al6061) for lap welding. Our main goal was to investigate the influence of these parameters on the weld bead profile and subsequently on the tensile shear strength of the joints. The tensile shear load was analysed in conjunction with elongation. It has been found that the joint's tensile shear strength was maximized (24.1 MPa, equivalent to 51.27% of the polycarbonate's strength) at a medium tool turning speed (1100 rpm) and medium joining speed (55 mm/min), which resulted from effective mixing at the joint interface. However, it's important to note that the weld bead profiles exhibited a blackish appearance at all rotational speeds. Non-uniform weld beads were particularly evident at higher rotational speeds and lower to medium traverse speeds, notably at 50 mm/min and 55 mm/min, respectively.