: Cotton yarns are widely used in manufacturing of various types of fabrics and apparels, due to their special physical and aesthetic properties. Cotton mélange yarns are produced from blending of dyed and grey cotton fibers with different blending ratios by one of two methods; blowing or drawing. This type of yarns have specialty dyed effects, similar to woolen vigore yarns that is not obtainable by yarn dyeing. In This work, aim at studying on cotton fiber damage and its effects on cotton mélange yarns properties, in production of rotor and ring mélange yarns with equal percentages (50/50). The cotton fibers were grade one sahel variety from gonbad which were used either in grey or dyed with benzonerol / VSF 600% direct dye. For mélange yarn production, grey cotton fibers were pre opened and then dyed. Dyed and grey cotton fibers were mixed either in blowing process or in drawing. To assess the fiber damage effect on the dyed and grey cotton fibers assemblies in yarns, 100% dyed and grey yarns were produced as well. After yarns production and random sampling, length parameters of dyed and grey fibers such as effective length, short fiber content were measured. Also elongation at break, strength, imperfections, unevenness and hairiness of produced yarns were examined. The results show that dyeing and mechanical process lead to decrease of effective length, increase of short fiber content. Increasment of short dyed fibers in rotor and ring mélange yarn cause the drop in mechanical properties such as tenacity and elongation at break, increased imperfections and unevenness and hairiness in mélange yarn. Also fiber damage in rotor mélange yarn is more than ring mélange yarn due to the further opening by opening roller. These variations are indicative of damage in dyed cotton fibers on mélange yarn manufacturing. SEM micro graphs confirms that fiber damage occurance in dyed cotton fiber. Evaluations of color blending uniformity of mélange yarns and fabrics show that the best color uniformity is resulted in blowing method and rotor spinning system. Also the least color uniformity is resulted when fibers are blended by drawing on ring spinning system.