Chlorococcum humicola (Nag) Rab. isolated from soil polluted with waste water at Sohag district was used as test organism in this investigation. The alga was grown in BG-11 medium containing different Cu2+ concentrations (0.0, 0.5, 50, 100, 150, 200 and 250 μM Cu SO4) and the lethal dose was 300 μM Cu SO4. The low concentration (0.5 μM) of Cu2+ caused an increase in growth {cell numbers, dry mass } and photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids). On increasing the Cu2+ concentrations, the cell number, dry weight and photosynthetic pigments were decreased. Moreover, total free amino acids were also inhibited with increasing Cu2+ concentrations. The protein content remained more or less unchanged even at the higher doses of the copper. Nitrate-reductase activity and phenolic compounds were decreased with increasing Cu2+ dose. On the other hand, Cu2+ stimulated the proline content, soluble proteins, lipoperoxides and ascorbate. The production of new polypeptide bands were appeared at the level of 150 μM Cu SO4 (70, 28, 26, 25 KDa). The results obtained indicated that, Chlorococcum humicola might be tolerated the pollution with Copper in soil.