Sidr (Ziziphus spina-christi) leaves powder was tested extensively to find out its ability as cadmium ions adsorbent. Parametric studies were carried out in a batch system and the results showed that removal efficiency increased to 98% when using an adsorbent dosage of 2 g L−1 and stayed high when the initial concentration was less than 100 ppm. Adsorption temperature might be maintained at less than 40 °C and the recommended pH was found to be in the range of 4.5–5.5. The main and effective functional groups detected on the surface of the adsorbent by using Fourier transform infrared spectroscopy were carboxylic acid, alcohol, nitro and alkyl halides groups. Isotherm equilibrium results depicted that the sequence of model fitness to experimental data (based on R2) was: Langmuir > Freundlich > Harkin-Jura > Jovanovic > Temkin > Dubinin –Radushkevich. Linear and non-linear equilibrium, and kinetics models were experienced. Maximum metal uptake, 95.2 mg/g was evaluated using a linearized form of the Langmuir model having higher R2 than a non-linear model. Kinetic and thermodynamics predictions revealed that mass transfer across the aqueous boundary layer, intra-particle diffusion, and exothermic pseudo-first-order reaction on the adsorbent surface were the main mechanisms of Cd(II) adsorption on the present adsorbent. Ten adsorption-desorption cycles were performed to evaluate the adsorbent reusability. In conclusion, the novelty of this work represents the successively chosen of sidr leaves as a new, abundant, low-cost, and favorable adsorbent for the removal of cadmium cations from aqueous solutions.