Eighteen Turkish breed Lambs of five months old were studied in this study, they were divided into two groups, control and infested, each group subdivided into three replication. Three animals were allocated in each replication of infested groups. Control group animal were dewormed and housed in pens. They were provided with a uniform management. Blood samples were collected from the jugular vein of each animal at monthly intervals for 5 months and were weighted for body weight gain. Hemoglobin (Hb) concentration was determined using hemoglobinometer, total white blood cells (WBC) and total red blood cells (RBC) were measured by hemocytometer method. This study shows that control group significantly (P<0.05) increased body weight gain, hemoglobin concentration and RBCs counts than infested group. H. contortus infection did not significantly influence the total WBCs counts between control and infested groups. Overall results demonstrated that Haemonchus contortus reduce the growth of Lambs.