The magnetic response, microstructural and texture changes occurring during cold rolling of a Fe−14Mn−0.64C−2.4Al−0.25Si medium stacking fault energy TWIP (twinning induced plasticity) steel have been studied by X-ray diffraction and magnetic techniques. The changes in the sub-grain size (D s ), probability of stacking fault formation (P sf ) and microstrain in the material as cold rolling progressed were determined by using a modified version of the Williamson and Hall equation. A strong development of the crystallographic texture with increasing deformation was observed. Deformation-induced formation of a small fraction α′-martensite was observed, indicating that the steel also exhibits γ → α′-martensite transformation during cold rolling, which is discussed via the changes of the stacking-fault probability and the texture development during cold rolling.