Posidonia oceanica (L.), a marine biomass, has been used as an effective and efficient biosorbent for the removal of Cd(II) from aqueous media. The physico-chemical properties of biosorbent were investigated by elemental analysis, BET surface area, FT-IR, SEM and EDX methods before and after adsorption. Batch adsorption experiments were carried out to investigate the effects of solution pH, dosage of biosorbent, contact time and temperature. The biosorbent exhibited the maximum uptake of 58.82 mg/g under the optimal adsorption condition. Kinetics experiments indicated that the pseudo-second-order model displayed the best correlation with adsorption kinetics data. Besides, experimental data could be better described by the Langmuir isotherm model. Desorption experiments were carried out to explore the feasibility of regenerating the biosorbent. The regeneration efficiency was 96.03 % using desorption agent of 0.2 M HCl. The thermodynamic parameters (ΔH 0, ΔS 0 and ΔG 0) of the cadmium ion uptake onto P.O indicated that the process is endothermic and proceeds spontaneously. The findings of the present study indicate that P.O can be successfully used for separation of Cd(II) from aqueous solutions. The results suggested that the adsorbent is promising for use as an effective and economical adsorbent for Cd(II) ions removal.