TWIP steel containing 0.21% C, 24.4% Mn, 0.9% Si, 1.84% Al, 4.61% Cr, 1.89% Ni, 0.41% Mo and 0.012% Nb was investigated. Tensile tests of this steel were performed in the strain rate range of 10−4–10−3 s−1. Results indicate that tensile properties of TWIP steel at room temperature are sensitive to strain rate in the studied range. Analyses on the relationship between strain–hardening exponent and strain rates show that the formation of twins during deformation greatly affects the strain–hardening behavior of TWIP steels.