In this paper, the effect of aqueous glycine treatments at different pH on the tensile properties of cotton fibers is reported. The effects on linear density and X-ray diffraction crystallinity were also evaluated. Glycine treated fibers at alkaline pH (i.e. at pH 11) produced fibers with higher linear density than control (untreated) and glycine treatments at acidic pH. The same treatment also increased strain values in cotton fibers by as much as 36%. Interestingly, similar changes in strain were observed under acidic conditions, especially at pH4, although the changes were smaller. Specific stress values normalized by the linear density measurements were not significantly different from control samples. The results of this research demonstrated improved strain properties of cotton fibers after aqueous glycine treatment at suitable conditions.