This investigation was conducted to study the effects of copper on growth and metabolism of Ankistrodesmus falcatus isolated from sewage water at El-Dare Treatment Plant. The alga was grown in BG-11 medium containing different cu concentrations (0.0, 0.5, 5, 10, 50, 100, 150, 200 and 250 µm Cu⁺²). The test organism was left to grow for 12 days under the various cu levels. The effect of copper on the growth, photosynthetic pigments, protein metabolism (soluble, insoluble), antioxidant compounds (phenolic, Proline) were determined. The cell number and dry weight were increased highly significantly up to 10 µm Cu⁺²), then the cell number and dry weight reduced gradually by increasing the doses of the copper .The concentration of photosynthetically active pigment peaked up to 10 µm Cu⁺²), Then they remained more or less unchanged up to 50 µm Cu⁺²) , after this it was reduced . The content of soluble carbohydrates decreased dramatically up to 10 µm Cu⁺², and then it was increased smoothly as the cu concentration increased in culture media. Cu Stress induced a significant changes in the soluble protein up to the level of 10 µm Cu⁺², then a high significant accumulation was obtained which peaked at the highest concentration of Cu⁺² (250 µm). The insoluble and total proteins remained more or less unchanged at the all Cu concentration used. Aminoacids content accumulated progressively and irregularly by Cu treatment. While proline content decreased by about 65.6% at the level of 10 µm Cu⁺² concentration. It is on other hand increased by 261.7% at the level of 250 µm Cu⁺² in relation to control value. Phenolic compounds seemed to be not affected by copper treatment.