It was shown that new high-manganese austenitic steels can be used as an alternative to conventional Ni–Cr austenitic steels especially in vacuum vessels. In this study, a nickel-free austenitic steel with chemical composition of 24 wt.% Mn, 10 wt.% Cr, 0.13 wt.% C and trace elements of Si, Ti, V, W, and Al was hot-rolled at 950 and 1100 °C to different strains. Microscopic observations, X-ray diffraction, tensile, impact and microhardness tests were performed to characterize the microstructural aspects and mechanical properties. A small amount of chromium carbide was found on the grain boundaries of this fully austenitic steel. The results showed that the microstructure and mechanical properties of hot rolled manganese austenitic steel are affected by the dynamic recrystallization and twinning phenomena. Also, by changing the grain morphology from equiaxed to elongated, strength and hardness increased, and the impact toughness and ductility were reduced.