Samanea saman barks which have been chemically modified in acidic condition were used as adsorbent for the removal of ferrous ions from aqueous solution. The adsorbent was characterized by SEM images, FT-IR and XRD analysis. Effecting parameters like initial pH, initial concentrations of metal ions and contact time were investigated. The adsorption data were well fitted by Langmuir and Freundlich isotherm model. Kinetic data were best described by Reversible First - order model. Thermodynamic studies showed spontaneous and endothermic nature in the adsorption of Fe (II) ions by the modified acid activated Samanea saman barks.