The effect of multiple forging and annealing on the microstructure and mechanical properties of a high-manganese steel is considered. An austenitic high-manganese steel, Fe-0.03C-28Mn-1.5Al (all in wt.%), with an average grain size of about 37 µm was used as the initial material in this study. Multiple forging at room temperature was carried out up to a total true strain of 2. Multiple forging was accompanied by deformation twinning and resulted in significant strengthening. The steel samples subjected to multiple forging demonstrate an increase in the strength properties with an increase in the total strain, while elongation decreases. After multiple forging to a total strain of 2, the samples were annealed at temperatures from 673 to 1073 K for 30 minutes. An increase in the annealing temperature leads to a decrease in the strength and a significant increase in plasticity. Annealing at temperatures of T = 873 K leads to the formation of a recrystallized microstructure.