A Deform^TM-3D analysis was used to illustrate the effect of strain rate on isothermal deformation (forging) of X20CrMoV121 steel. The simulation process was conducted at an isothermal temperature of 850 °C and varying the strain rates of 1.9 s^-1, 2 s^-1 and 3 s^-1. The results of temperature, strain and stress distribution at various strain rates were reported. The strain/stress distribution exhibited a heterogeneous distribution, indicating inhomogeneity during hot forging. It was also shown that the deformation inhomogeneity decreased with the increase in the strain rate. The results are comparable to experimental publications, indicating that Deform^TM-3D is an effective tool for finite element analysis of hot deformation processes.