Twenty four Ossimi lambs aged  4 months and averaged  20.2 ± 1.53  kg of body weight were randomly allocated  to three equal groups . All groups were fed a basel diet ( containing 10 ppm copper ) of concentrate mixture and Alfalfa as the    rate of 3 and 1 % of body weight , respectively .  The three groups were assigned at random to receive either the basel diet alone or supplemented with either 15 or 30 ppm Cu   . Body weight gain, nutrient digestibility coefficients, feed conversion and economical evaluations were determined.  Blood samples were taken and analyzed for hemoglobin (Hb), packed cell volume (PCV), red blood cells count (RBCs), total white blood cell count (WBCs) and  differential leukocytes percentages .  The results showed that lambs of G2 and G3 had higher values of daily weight gain, nutrient digestibility coefficients, nutritive values and feed conversion than control.  Red blood cells ( RBCs), hemoglobin concentration (Hb) and packed cell volume (PCV)  increased in lambs of G2 and G3 compared to control group.  Lambs of G2 and G3 recorded higher values of a total leukocytes count and a marked increase in both lymphocytes and esinophils accompanied with a drop in percentage of neutrophils.  Meanwhile percentage of the basophiles and monocytes did not change in the  treated lambs.  These results revealed that supplementation of copper might have useful role in enhancing growth performance and immune responses for growing lambs. This matter needs further detailed studies .