<p>Sc is commonly used as a strengthening element in Al-Si casting alloys, but its influence mechanism on hot tearing is still unclear. In this work, the effect of minor addition of Sc on the hot tearing performance of alloys was studied through a custom-made experimental device, and after the initial hot tearing point temperature and load were compared, the hot tearing sensitivity of alloys with different Sc contents was evaluated. The results were consistent with the visual observation of crack severity. The results show that minor Sc addition can reduce the hot tearing sensitivity of Al-Si-Cu alloy, but with a further increase in the amount of added Sc, the hot tearing sensitivity of the alloy increases. The microstructure morphology shows that the addition of Sc can refine the α-Al grain size and generate new W-Al₈-xCu₄ + xSc and Al₃Sc. Al₃Sc changes the precipitation position of the <i>θ</i>-Al₂Cu phase, which is not conducive to avoiding the occurrence of hot tearing. Furthermore, when Sc is used to refine the grains but fails to refine them into equiaxed grains, Al₃Sc acts as a heterogeneous nucleation site for α-Al, which leads to an increase in the formation time of the dendritic skeleton and reduces the liquid phase shrinkage time. On the other hand, Sc has a strengthening effect on the alloy skeleton, enabling it to resist higher shrinkage loads and helping to avoid the formation of hot tearing.</p>