An experimental study on the removal of Cu(II) from aqueous solutions by D151 resin was carried out in a batch system. The response surface methodology (RSM)-guided optimization indicated that the optimal adsorption conditions are: temperature of 35 °C, pH of 5.38, and initial Cu(II) concentration of 0.36 mg/mL, and the predicted adsorption capacity from the model reached 328.3 mg/g. At optimum adsorption conditions, the adsorption capacity of Cu(II) was 321.6 mg/g, which obtained from real experiments what were in close agreement with the predicted value. The adsorption isotherms data fitted the Langmuir model well, and the correlation coefficient has been evaluated. The calculation data of thermodynamic parameters (ΔG, ΔS, and ΔH) confirmed that the adsorption process was endothermic and spontaneous in nature. The desorption study revealed that Cu(II) can be effectively eluted by 1 mol/l HCl solution, and the recovery was 100%. Moreover, the characterization was undertaken by infrared (IR) spectroscopy.