Abstract: The effect of copper sulfate in the regulation of molt and gonad development in the shrimp Litopenaeus vannamei was investigated. Initially, we determine the copper sulfate safe level for use in culture medium shrimps. Six concentrations of copper sulfate (0, 0.01, 0.05, 0.1, 0.2, 0.5 mg L-1) were tested in 10 L glass aquaria for 15 days. After 15 days, survival of the control treatment (0% CuSO4) averaged 100%. The survival in 0.01, 0.05, 0.10 and 0.20 mg L-1 (100, 100 and 98%) concentrations of CuSO4 were significantly greater than the higher dose treatment (0.50 mg L-1 CuSO4; survival 43%). The copper (0.05 mg L-1) exposed shrimps accelerated the molting (premolt stage: female, 100%; males, 90%). The copper (0.10 mg L-1) exposed shrimps accelerated the both molting and reproduction (premolt stage: female, 50%; males, 40%). The copper (0.20 mg L-1) exposed animals significantly (p<0.0001) increased mean oocyte diameter and testicular follicle diameter as well as mean gonad indices from the control as well as other treated shrimps. These results provide strong evidence that trace amount of copper is an essential for both molting and reproduction in shrimps.