Magnesium (Mg) alloys offer the potential to revolutionize transportation, manufacturing, electronics, and biomedical devices due to their distinct characteristics including low density, high load capacity, and high specific modulus. However, at low temperatures, the ductility of Mg alloys is compromised because of their dense hexagonal structure and slip-limiting system. In this study, we investigated the effect of the MDF process on superplastic behavior of cast AM60 Mg alloy. The alloy’s grain structure undergoes significant refinement, leading to its grain size measuring 1.9 µm after completing 8 passes through the MDF. Then AM60 Mg alloys were assessed for their superplastic properties through shear punch tests (SPT) at elevated temperatures and different strain rates. From the SPT results, m-values of 0.25, 0.25, 0.29, and 0.42 were obtained for 2, 4, 6, and 8 MDF passes, respectively. The m-value of 0.42 after 8 MDF passes suggests the occurrence of intergranular sliding as the mechanism behind superplastic deformation.