<p>Understanding the fatigue behavior of tungsten inert gas (TIG) welds of dissimilar aluminum alloys is crucial for ensuring structural integrity across various industries. Constant amplitude fatigue tests were conducted on TIG butt-welded joints of dissimilar 6061 and 7075 aluminum alloys using the MTS809 system. Subsequently, typical fatigue fractures were examined under a TESCAN VEGA3 scanning electron microscope (SEM). The fatigue tests revealed that some specimens failed at the weld toe on the 6061 side, while others fractured at the faying faces of the two sheets where they were butt-welded together. Upon examination, defects such as lack of fusion and pores were identified. Experimental observations demonstrated that specimens tended to fail at the weld toe under relatively low loading, and at the faying faces under higher loading. To assess the fatigue life of the welded joints, both the notch stress method and hot-spot stress method were employed, in conjunction with finite element stress-strain analyses. A comparison between the predicted fatigue life results and experimental test results indicated that the faying faces at the sheet ends behaved like a weak connection. The notch stress method could provide more agreeable life evaluation results within the low-cycle fatigue regime, whereas the hot-spot stress method demonstrated better suitability for high-cycle regime fatigue life evaluation.</p>