This study presents a comprehensive investigation of the friction spot joining (FSpJ) process for joining aluminum alloy sheets (AA6061 and AA5052) with polymeric materials, including polyether-ether-ether-ketone (PEEK) and short glass fiber-reinforced polyphenylene sulfide (GF-PPS). The influence of process parameters, surface treatment, and material characteristics on joint interface morphology, tensile-shear strength, temperature distribution, and failure mechanisms were systematically examined through experimental and numerical approaches, including response surface method (RSM) analysis and three-dimensional (3D) finite element simulations. Results showed that the peak temperature at the interface could reach up to 400°C for AA6061-PEEK joints and 428℃ for AA5052-GF-PPS joints. Optimal combinations of spindle speed, plunging depth, and dwell time yielded tensile-shear peak loads of 4576 N and 4426.5 N for the respective materials. Surface treatment, such as Boehmite treatment for aluminum sheets, significantly improved joint strength, and joint failure mainly occurred in the polymeric base materials. Microscopic and macroscopic interlocking mechanisms contributed to desirable bonding strength. This study highlights the potential of the FSpJ process for joining metallic and polymeric materials, providing invaluable insights into the optimization of process parameters and understanding of joint characteristics, which can be extended to other material combinations.