A comparative study of copper (Cu) and lead (Pb) treatments to Ulva lactuca introduced from Damietta harbor, was conducted by examining dry weight and pigmentation, total soluble sugars, protein, ascorbate and superoxide dismutase. The lower concentrations of Cu and Pb (0.01 and 0.1 mg l^-1 respectively) increased contents of chlorophylls, carotenoids, and total soluble sugars, and also induced a strong activation of antioxidant activity in U. lactuca. However, concentration (0.1 mg l^-1) of Pb exhibited a non significant change of dry weight and protein from untreated control. Whereas concentration (1 mg l^-1) of both Cu and Pb induced both of enzymatic (Superoxide dismutase) and non enzymatic (Ascorbate) antioxidants, but inhibited dry weight and contents of carotenoids, protein and total soluble sugars in U. lactuca. In the other hand, chlorophylls (a and b) were induced in case Cu treatment but were inhibited in case Pb treatment at the same concentration (1mg l^-1). Although, higher concentration (5 mg l^-1) of both Cu and Pb seemed to be toxic and inhibited most metabolic activities, it induced enzymatic antioxidant (Superoxide dismutase). However, Cu seemed advantageous to growth and physiological responses of U. lactuca than Pb. Both heavy metals particularly at the lowest concentrations are beneficial to U. lactuca growth and for production of antioxidants.