Structural reorientations in metallic fcc nanowires are controlled by a combination of size, thermal energy and the type of defects formed during inelastic deformation. By utilizing atomistic simulations, we show that fcc nanowires can exhibit shape memory and pseudoelastic behavior that was previously believed to be limited to exotic alloys such as NiTi. We also show that the formation of defect free twins, a process related to the material stacking fault energy, is the mechanism that controls the ability of fcc nanowires of di•erent materials to show reversibility in loading and thus shape memory and pseudoelasticity. The ability of nanowires comprised of traditional metallic materials to show shape memory and pseudoelasticity has significant scientific and technological implications.