Agaricus campestris was used as an adsorbent for the adsorption of Cu(II) ions in water. The adsorption process was carried out in a batch process and the effects of contact time, initial pH, initial Cu(II) ion concentration, adsorbent amount, and temperature on the adsorption were investigated. Kinetic calculation results from the recent experiments showed that the amount of adsorbed Cu(II) increased with increasing Cu(II) concentration, pH, temperature, contact time and with decreasing adsorbent amount. Pseudo-second-order reaction model provided the best description of the data with a correlation coefficient 0.99-1 for different initial metal concentrations and temperatures were studied. The equilibrium data were well fitted to the Langmuir isotherm. The maximum adsorption capacity for Cu(II) was 32.52 mg g-1 at 298 K. Thermodynamic parameters such as ΔH 0, ΔS 0 and ΔG0 were calculated. The adsorption process was found to be endothermic and spontaneous. © 2010 American Institute of Chemical Engineers Environ Prog, 2011 Copyright © 2010 American Institute of Chemical Engineers (AIChE).