Swelling behavior of cotton, dissolving wood pulp (DWP), viscose staple fibre (VsF), and Tencel staple fibre (TsF) in varying sodium hydroxide (NaOH) were investigated by means of optical microscopy and were characterized by molecular mass distribution, X-ray diffractometer, and dynamic vapor sorption. Effect of temperature (20-45 °C) and duration (0-120 min) was studied. The results reveal that the swelling ratio of fibre in alkali solution depends on fibre accessibility and NaOH concentration. Among all the materials, VsF exhibited the highest swelling ratio and lowest swelling ratio has been observed for cotton fibre. The results suggest that the swelling is limited by the presence of plant cell wall structures in cotton and DWP, rather from fringed-fibrillar, semi-crystalline sub-structures, which result from the inherent tendency of cellulose molecules to form such structures during the biosynthesis of plant cell walls as well as during the formation of regenerated cellulosic textile fibre in wet-spinning.