Tencel fabrics were treated with NaOH, mechanically fibrillated, and hydrolyzed by cellulase. X-ray diffraction method, moisture regain, and K/S value were used to elucidate crystalline structural changes brought about by cellulase treatment. Degree of polymerization and copper number of the cellulase-treated fabrics were also measured to estimate the effect of hydrolysis. X-ray diffraction studies showed that crystalline structure and degree of crystallinity were not much changed by cellulase treatment. On the other hand, as cellulase hydrolysis progressed, moisture regain and K/S value increased slightly due to the increase in specific surface area from formation of fibrils. The degree of polymerization initially decreased with enzymatic hydrolysis and then levelled off. Copper number increased, however, to a great extent at initial stages of cellulase hydrolysis and decreased gradually. The NaOH-pretreated fabrics resulted in higher degree of crystallinity, degree of polymerization, moisture regain, and K/S value, but lower copper number than those of the fabrics without NaOH pretreatment at the same cellulase treatment conditions. These results were attributed to extraction of short molecular chains from amorphous region during NaOH pretreatment and the opening of the structure of the amorphous region.