Adsorption potentials of native and amine-modified plant biomass of Alyssum caricum for the removal of Reactive Green 19 (RG-19) and Reactive Red 2 (RR-2) dyes from aqueous solutions were studied. The adsorbents were characterized before and after modification process using Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and potentiometric titration analysis. Modification of the surface of A. caricum biomass with hexamethylenediamine (HMDA) showed an increase of 1.18-fold in its surface area. Batch studies illustrated that dye adsorption were highly dependent on different process variables, pH, initial dye concentration of solution, adsorbent dosage, and temperature. The maximum adsorption capacities of the native and amine-modified adsorbents were 27.6 and 63.4 mg/g adsorbent for RG-19 dye and 16.5 and 36.8mg/g adsorbent for RR-2 dye, respectively. The adsorption of both dyes on the native and amine-modified plant biomass correlated well with the Langmuir and Temkin isotherm equations as compared to Freundlich and D-R equations. The calculated thermodynamic parameters for both native and amine-modified adsorbents showed that the adsorption was feasible, spontaneous, and exothermic. The information gained from these studies was expected to indicate whether native and amine-modified adsorbents can have potential to be used for the removal of other dyes from wastewaters.