AbstractFriction Spot Joining is an innovative friction-based joining technique for metal–polymer hybrid structures. In this work, aluminum alloy 2024-T3 and CF-PPS friction-spot joints were produced with additional PPS film interlayer. The joints were investigated in terms of the microstructure, mechanical performance under quasi-static loading and failure mechanisms. Macro- and micro-mechanical interlocking as well as adhesion forces were identified to dictate bonding mechanisms in the FSp joint with film interlayer. The ultimate lap shear force of the joints (2700 ± 115 N up to 3070 ± 165 N) were 20%–55% higher than the corresponding joints without interlayer, due to the larger bonding area, better load distribution and improved micro-mechanical interlocking. The failure analysis of the joints revealed a mixture of adhesive-cohesive failure, whereas cohesive failure was dominant.