Variation of the stacking fault energy in FCC alloys and austenitic steels is well known to influence the evolution of radiation damage and its effect on deformation mechanisms. The primary defects observed in austenitic steels under neutron irradiation are mainly Frank loops. Here, we study the interaction of edge and screw dislocations with Frank loops in low stacking fault energy Fe–Ni alloys. The interatomic potentials employed were specially developed to reproduce a number of properties of real austenitic steels. The influence of temperature and loop morphology on the interaction mechanism and the critical resolved shear stress for dislocations to overcome loops has been investigated. All investigated reactions have been subdivided into three classes depending on temperature, loop size and interaction geometry. It is shown that by decreasing stacking fault energy below a certain value the formation of constrictions on dislocations is suppressed so that loop unfaulting becomes a less favorable mechanism in comparison with loop shear. Additional effect of solid-solution alloying, causing a non-negligible friction stress, is expressed in the impedance of the propagation of dislocations in the secondary glide planes, which is another factor limiting the unfaulting process.