The present study found that the work-hardening rate and dislocation density in a twinning-induced plasticity (TWIP) steel deformed at 373 K and 473 K are comparable to that deformed at 298 K, but deformation twins are considerably prohibited at 373 and 473 K. High dislocation density induced by dynamic strain aging (DSA) is the dominant mechanism responsible for the high work-hardening rate of TWIP steels at 373 and 473 K. It indicates that TWIP steels can also achieve high working-hardening rate without the formation of deformation twins.