The aim of this study was to determine the effects of zinc oxide administrations on body weight gain and some biochemical parameters (zinc, copper, iron, calcium, magnesium, total protein and gammaglobulin) in the blood serum of lambs. This study was performed on 35 Ivesi male lambs (control group: 15, experimental group: 20), aged between 20 and 25 days. In the experimental group, 500 mg zinc oxide (2% solution) was administered orally 12 times with period of a week. Blood samples were collected on days of 0, 14, 28, 42 and 84. Furthermore, body weights of the lambs were determined on days of 0, 14, 28, 42, 56, 70, 84 and 118. The mean serum zinc and gammaglobulin levels in all periods after zinc administrations in the experimental group were significantly higher than those in the control group. Also, body weights of the experimental group on days of 70, 84 and 118 were significantly higher than those of the control group. However, copper values in the experimental group were significantly lower on days of 28, 42 and 84 than those in the control group. There were no significant differences in iron, calcium, magnesium and total protein levels between two groups. In conclusion, oral zinc oxide administration caused significant increases in body weight gain and serum zinc and gammaglobulin levels in lambs. Zinc and copper combinations were concluded to be more useful than zinc given alone. Because zinc administration alone might cause decreases in serum copper values of lambs.