This study compares and optimizes the friction stir clinched and friction stir spot welded hybrid aluminum/acrylonitrile butadiene styrene polymer (Al/ABS) joints. The mechanical and fracture behaviors of the respective hybrid joints were investigated. The results show that the friction stir spot welded Al/ABS joint exhibited a higher tensile-shear failure load. The presence of higher deformation (protrusion-aided) and deeper tool profile-induced hole (stress raiser) in the friction stir clinched Al/ABS joint impaired the loadbearing resistance of the joint. The optimum tensile-shear failure loads of the friction stir spot welded, and friction stir clinched Al/ABS joints are 932 and 509 N respectively. Three fracture modes, namely unbuttoning, circumferential-partial Al in-polymer shearing, and mid-nugget shearing modes, ensue in both joint categories. Protrusion-aided deformation is not desirable for the improved performance of the hybrid Al/ABS joint. Friction stir spot welding is thus recommended for the fabrication of hybrid metal/polymer.