The production of polyester fibers has been dynami‌cally increased, accompanied by the common use of polyester-cotton blends. In this research work, polyester (100%), cotton (100%), and polyester-cotton blend fabrics (50/50) have been subjected to treat with caustic soda, chitosan and their hybrid, followed by one-bath two-stage dyeing with reactive dye (Reactive Red 198 RR198), to study their dyeing performance and morphology. SEM images of polyester treated and untreated with caustic soda, it describes the ease of adsorption on the alkaline modified fabric surface. The one bath two step method was used to shorten the dyeing process, increase yield and reduce the utility and chemical cost. In the final stage, the dyed fabrics were tested for color strength (K/S) value, dye intensity, fixation% in addition to, fastness properties evaluated by testing the light, washing and perspiration fastness properties of the dye. The results clearly show that for all pre- treated fabrics using caustic soda (90 g/dm3 of caustic soda, 100 min ; 80oC), favorable absorption of reactive dye RR198, resulting a high color strength and fixation % due to surface modification of polyester and mercerization of cotton fabrics. The effect of chitosan pretreatment on dyeability, fastness, and some physicochemical properties has been investigated. Hybrid treatments of textile materials by combining alkali and chitosan are potentially the most effective for improved dye color strength and fixation % and it could be applied as a novel approach to textile dyeing and finishing.