ABSTRACT Fatigue analysis of swept friction stir clinch (Swept-FSC) joints between 6061-T6 aluminum (Al) and S45C steel (Fe) sheets was conducted through experimental approaches. Before fatigue tests, the welding tool was first modified to eliminate the hook structure inside the Swept-FSC joint. A parameter study for the indentation depth and re-indentation depth was conducted to obtain appropriate process parameters and improve the mechanical properties of Swept-FSC joints. After the lap-shear (LP) and cross-tension (CT) specimens were made, a series of quasi-static and fatigue tests were conducted. The fatigue data of Swept-FSC joints were recorded. The fatigue behavior of Swept-FSC joints in LP and CT specimens were examined through optical and scanning electron microscopes. Experimental results indicated that LP specimens have three failure modes, while CT specimens have only one failure mode.