A total of 120 one day-old Nicholas turkey chicks were divided randomly into six equal groups. The first and second groups were treated with distilled water (once and twice weekly) and served as control (T1 and T2), the third and forth groups (T3 and T4) were treated with 5% potassium iodide (KI) solution once and twice weekly, respectively, while fifth and sixth (T5 and T6) groups were treated with 10% potassium iodide (KI) solution once and twice weekly, respectively. The treatments were spraying over chick heads. The chicks were kept at rearing wire cages, and the feed and water were available ad libitum. At 45 days of age ten birds from each group were intramuscularly injected with 0.5 ml of SRBCs. The obtained results showed that chicks sprayed with 10% KI showed the highest LBW and gain (P<0.05) at 30, 45 and 60 days of age, followed by 5% KI, while the control showed the lightest weights and gain. LBW and gain of chicks at 60 days of age was higher (P<0.05) for spraying once than twice/week. Both KI levels increased (P<0.05) WBCs count and blood hemoglobin (Hb) concentration as compared to control. Chicks in 10% KI treatment showed the highest (P<0.05) WBCs count and Hb concentration. WBCs count was higher (P<0.05) by spraying the chicks twice/week than once/week. RBCs count and Hb concentration were nearly similar as affected by spraying time. Serum total protein (TP) concentration increased (P<0.05) with 10% KI as compared to control, but did not differ from that with 5% KI.  Globulin (GL) concentration increased (P<0.05) and albumin (AL) was not affected by 10% KI. However, AL/GL ratio increased (P<0.05) with 5% KI as compared to control, but did not differ from that with 10% KI. There were insignificant differences in AST and ALT activities. Serum T3 concentration was the highest (P<0.05) with 10% KI, followed by 5% KI and the lowest in control, respectively. T3 concentration was higher (P<0.05) by spraying twice than once/week. Chicks treated with 10% KI showed the highest (P<0.05) antibody titer and the lowest (P<0.05) lysozyme concentration, followed by 5% KI, while the control showed the lowest antibody titer and the highest lysozyme concentration (P<0.05). Spraying twice/week increased (P<0.05) antibody titer and decreased lysozyme concentration, reflecting the highest immune response for chicks treated with 10% KI twice/week. It could be concluded that potassium iodide had positive effect on turkey chicks when used as spraying over heads of growing chicks with 10% once a week.