Abstract Radiation-induced defects are the significant cause of radiation damage in austenitic stainless steels. In this work, the interactions between a screw dislocation and stacking fault tetrahedrons (SFTs) are studied in Fe–10Ni–20Cr (a model alloy of austenitic stainless steel) and Ni, using molecular dynamics simulations. Four interaction processes were primarily found, including (1) partial absorption, (2) sheared, (3) bypassing, and (4) restored through double cross-slip. In Fe–10Ni–20Cr alloys, there is almost no correlation between the critical resolved shear stress (CRSS) value and SFT size, but the intersection position largely impacts the results. And the CRSS value decreases with temperature increasing in Fe–10Ni–20Cr. The occurrence of cross-slip has a significant effect on the interactions, and there exist greater CRSS value in the interactions of cross-slipping. Besides, the occurrence of the cross-slip is linked to the stacking fault energy and the distribution of solute atoms of the alloys.