Effect of strain rate on the tensile behavior of two friction stir-processed dual-phase high entropy alloys was investigated. The dual-phase high entropy alloys have a high fraction of metastable f.c.c. phase. Engineering the f.c.c. phase metastability through alloy chemistry leads to different levels of transformation and impacts the retained f.c.c. phase after deformation. These metastable high entropy alloys show dominance of transformation-induced plasticity (TRIP) irrespective of strain rates, unlike the observations in TRIP steels. © 2020, The Minerals, Metals & Materials Society and ASM International.