The origin and role of ∑3 boundaries during dynamic recrystallization (DRX) and grain boundary engineering (GBE) of a Ti-modified austenitic stainless steel (alloy D9) is studied. Hot deformation tests were carried out on solution-annealed (SA) specimens to study the DRX behavior whereas a series of cold deformation and annealing were performed on SA specimens to realize GBE microstructure. A linear relationship between the area fraction of DRX and the number fraction of ∑3 boundaries was observed during hot deformation. This high fraction of ∑3 boundaries could account for the formation of coherent annealing twins by "growth accidents" during DRX. For certain combinations of cold deformation and annealing, a significant increase in ∑3 boundaries was observed. In contrast to hot deformation, majority of these new ∑3 boundaries during cold deformation and annealing were formed by geometrical interactions between the pre-existing ∑3 boundaries. The role of the ∑3 boundaries during DRX and on tailoring microstructure through grain boundary engineering approach is discussed. © (2012) Trans Tech Publications, Switzerland.