The litter of natural trembling poplar (Populus tremula) forest (LNTPF) was used for the biosorption of Cu(II) ions in a batch adsorption experiments. The sorption capacity of LNTPF was investigated as a function of pH, particle size, agitating speed, initial Cu(II) concentration, adsorbent concentration and temperature. The efficiency of copper uptake by the used LNTPF increases with a rise of solution pH, adsorbent concentration, agitating speed, temperature, and with a decline of particle size and initial Cu(II) concentration. The biosorption process was very fast; 94% of Cu(II) removal occurred within 5 min and equilibrium was reached at around 30 min. Batch adsorption models, based on the assumption of the pseudo-first order, pseudo-second order mechanism were applied to examine the adsorption kinetics. The pseudo-second order model was found to best fit the kinetic data. EPR studies combined with FTIR spectroscopy were used to represent the biosorption mechanism. Thermodynamic parameters such as DeltaH degrees, DeltaS degrees and DeltaG degrees were calculated. The adsorption process was found to be endothermic and spontaneous. Equilibrium data fitted well to Langmuir adsorption model. This study proved that the LNTPF can be used as an effective, cheap and abundant adsorbent for the treatment of Cu(II) containing wastewaters.