In the present study, the potential of the raw (RS) and NaOH-Modified Rice Straw (MRS) to remove copper (II) from aqueous solutions was investigated by batch tests under different experimental conditions. The chemical and morphological structures of adsorbents were investigated by scanning electron microscopy (SEM), energy Dispersive Analysis of X-rays (EDAX), element analyser and Fourier-Transform Infrared spectroscopy (FTIR). The study also investigated the effects of process parameters such as initial Cu (II) concentration, solution pH and temperature. Results of the present study revealed that, the maximum adsorption was about 39.40% and 46.20% for RS and MRS respectively, at pH 4.3, contact time 210 min. and initial concentration is 381.3 mg L–1. Langmuir and Freundlich adsorption isotherms were applicable to the absorption process and their constants were evaluated. The good correlation coefficient was obtained from pseudo second-order kinetic model, which agreed with conception as the rate-limiting mechanism. Thermodynamic aspects of the adsorption process indicated feasible, spontaneous and endothermic biosorption process. The modified rice straw in comparison, could adsorb Cu (II) ion faster than the unmodified.