A total number of 132 (108 females and 24 males) ducks of both Pekin and Domyati at 24 weeks of age were assigned randomly into four treatment groups with three replicates of each (9 females and 2 males), to evaluate the effect of iodine supplementation to the duck diets on productive and physiological performance during laying period. The four experimental groups were as follow: The control group (C) received basal diet contained 0.3 mg iodine/ kg diet, while groups 2, 3 and 4 received the basal diet supplemented with 1.0, 1.5 and 2.0 mg iodine/ kg diet, respectively. The obtained results could be summarized as follows: 1-The best (p≤0.05) egg number was recorded for Pekin ducks during the whole experimental periods. 2-The Domyati ducks recorded significantly heavier egg weight throughout the experimental periods compared to Pekin ducks. 3-Iodine supplementation (2.0, 1.5, and 1.0 mg/kg diet) resulted in a significant increase in egg weight at the whole experimental period compared to the control one. 4-The Domyati ducks fed diet contained 1.5 mg CaI/kg diet pronounced the best (p≤0.05) egg number/ duck and egg weight, whereas, Pekin ducks fed of 2.0 mg CaI/kg diet recorded the same trend in respect of  egg number and egg weight. 5-Birds fed 2.0 mg CaI/kg diet had the best value of feed consumption. 6-Birds fed 1.5 and 2.0 mg CaI/kg diet recorded significantly the best feed conversion ratio compared to other groups. 7-Iodine level treatments (1.0 and 2.0 mg CaI/kg diet) significantly  improved the hatchability of set and  fertile eggs compared to other treatment groups. 8-Dietary iodine supplementation, generally improved blood parameters and hematology traits without any adverse effects. It is concluded that dietary supplementation of excess iodine (Calcium iodate) at a level of 1.5 and 2.0 mg/kg diet to local Domyati breed and Pekin ducks diets, respectively could be recommended to improve their physiological and productive performance during laying period. A total number of 132 (108 females and 24 males) ducks of both Pekin and Domyati at 24 weeks of age were assigned randomly into four treatment groups with three replicates of each (9 females and 2 males), to evaluate the effect of iodine supplementation to the duck diets on productive and physiological performance during laying period. The four experimental groups were as follow: The control group (C) received basal diet contained 0.3 mg iodine/ kg diet, while groups 2, 3 and 4 received the basal diet supplemented with 1.0, 1.5 and 2.0 mg iodine/ kg diet, respectively. The obtained results could be summarized as follows: 1-The best (p≤0.05) egg number was recorded for Pekin ducks during the whole experimental periods. 2-The Domyati ducks recorded significantly heavier egg weight throughout the experimental periods compared to Pekin ducks. 3-Iodine supplementation (2.0, 1.5, and 1.0 mg/kg diet) resulted in a significant increase in egg weight at the whole experimental period compared to the control one. 4-The Domyati ducks fed diet contained 1.5 mg CaI/kg diet pronounced the best (p≤0.05) egg number/ duck and egg weight, whereas, Pekin ducks fed of 2.0 mg CaI/kg diet recorded the same trend in respect of  egg number and egg weight. 5-Birds fed 2.0 mg CaI/kg diet had the best value of feed consumption. 6-Birds fed 1.5 and 2.0 mg CaI/kg diet recorded significantly the best feed conversion ratio compared to other groups. 7-Iodine level treatments (1.0 and 2.0 mg CaI/kg diet) significantly  improved the hatchability of set and  fertile eggs compared to other treatment groups. 8-Dietary iodine supplementation, generally improved blood parameters and hematology traits without any adverse effects. It is concluded that dietary supplementation of excess iodine (Calcium iodate) at a level of 1.5 and 2.0 mg/kg diet to local Domyati breed and Pekin ducks diets, respectively could be recommended to improve their physiological and productive performance during laying period.