This study aimed to assess the effect of Napthalene Acetic Acid (NAA) on fiber quality parameters of cotton (Gossypium hirsutum L.). Field trials were carried out at the trial site of Arapoğlu Village in the Haliliye county of Şanlıurfa. A factorial randomized complete block design with three replications was employed. In the study, NAA applications were observed at the beginning of squaring (B.S.) stage (300, 600 and 900 g ha^-1), at the beginning of flowering (B.F.) stage (300, 600 and 900 g ha^-1) and at the flowering peak (F.P.) period (300, 600 and 900 g ha^-1). As a result of this study; It was concluded that the effect of NAA applications on fiber length and fiber strength was statistically significant but differed according to years and there was no stability in terms of these properties. There was no statistically significant effect of NAA applications on fiber maturity, fiber elongation, uniformity index, short fiber index, fiber reflectance and spinning consistency index.