Aim: The isotherms of the adsorption of nickel (Ni) (II) ions from model aqueous solutions with the initial concentration of metal ions from 0 to 1500 mg/dm3 by crushed bark, wood sawdust, and leaves of trees of Acacia auriculiformis in static mode are obtained. It has been established that crushed acacia bark has the largest adsorption capacity with respect to Ni II ions (7 mg/g), and the lowest adsorption capacity has acacia leaves (4 mg/g). Adsorption isotherms were calculated using Langmuir, Freundlich, Dubinin–Radushkevich, Temkin, Flory-Huggins, Harkins-Jura, and Frenkel-Halsey-Hill models. Materials and Methods: The sorption properties of leaves, sawdust of wood, and crushed bark of A. auriculiformis were studied in the static adsorption regime using model aqueous solutions of Ni sulfate (II) with initial concentrations of Ni2+ ions from 0 to 1500 mg/dm3. Results: It is found that the isotherms of the adsorption of Ni ions by leaves, wood sawdust, and crushed bark are most adequately described by the Dubinin–Radushkevich model with the approximation coefficients R2 = 0.988, R2 = 0.988, and R2 = 0.982, respectively, indicating that the process takes place both in the pores and on the surface of sorption material. The thermodynamic parameters of the adsorption process are calculated. Conclusions: The obtained values of Gibbs energy ΔG and the adsorption energy E indicate that the limiting adsorption stage of Ni (II) ions by A. auriculiformis components is physical adsorption.