Forty Egyptian Saidi pregnant ewes were used to study the effect of iodine supplementation on physiological responses and the metabolic rate of Saidi pregnant ewes and their lambs' performance until weaning. Ewes were divided into two equal groups (20 ewes per each), control group and treatment group which was treated with 12 mg iodine solution every 2 days from the beginning of the last third of pregnancy and the lambing was during winter. Body weight of ewes at the end of pregnancy was higher in iodine supplemented group compared to control (43.9 vs. 41.1 kg, P<0.05). Gas volume per minute, tidal volume and metabolic rate values were significantly higher in the treated group compared to control group. Serum total protein and its fractions in addition to glucose concentrations tended to increase with iodine supplementation. Also, serum T3 and T4 concentrations were higher (P<0.05) in iodine supplemented group compared to control group (5.47 ng/dl &120.7 ug/dl vs. 4.0 ng/dl and 76.7 ug/dl, respectively). In conclusion, iodine supplementation beneficially influences the physiological responses, the metabolic rate and some blood constituents of Saidi pregnant ewes which subsequently improved the performance and the survivability of their lambs.