Wastewater is environmentally damaged by textile industry due to dyes which are an important class of pollutants. This research explores the possibility of using the biopolymer chitosan and phosphogypsum a by-product of treating phosphate ore as adsorbents for the removal of disperse blue 165 from aqueous solution. Chitosan and Phosphogypsum were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. Optimum adsorption conditions were selected by varying the adsorbent dose, solution pH, initial dye concentration, and contact time. The results show that the removal of disperse blue 165 increases with increasing initial dye concentration and the equilibrium contact time were 60 min and 30 min for chitosan and phosphogypsum respectively. The adsorption isotherms were examined and the Langmuir model gives the best fit. Adsorption capacities were 103.09 mg.g-1 for chitosan and 6.79 mg.g-1 for phosphogypsum. Dynamic adsorption studies show that the adsorption reaction was well represented by the pseudo-first-order kinetic process for both adsorbents. The adsorption behavior was also tested using thermodynamic parameters.