Formation of ultrafine grained ferrite by warm deformation of tempered lath martensite was investigated in Fe–2Mn–(0.1–0.8)C (mass%) alloys. Analysis of initial microstructure shows that an increase in carbon content leads to a decrease of lath martensite block size. Fine equiaxed (α) grains surrounded by high-angle boundaries are formed by dynamic recrystallization. As carbon content increases, the recrystallized α grain size decreases. It is considered that dynamic recrystallization of tempered lath martensite is a continuous type.