Background: Grave's disease (GD) is an autoimmune disorder caused by the thyroid receptor antibodies (TRAb), resulting in hyperthyroidism and goiter with extrathyroidal manifestations as; Grave's ophthalmopathy, dermopathy and acropachy. Selenium: the essential trace element found to have a crucial role in the maintenance of thyroid physiology and function. Thus, selenium deficiency reported to be linked in the start and progress of autoimmune thyroid diseases in genetically predisposed individuals. The aim of the current to evaluate the selenium status by measuring serum selenoprotein P (SEPP) level in GD patients, in comparison to healthy subjects and assess the linkage between selenium status and Grave's ophthalmopathy (GO). Patients and methods: A case control study that was conducted on 80 subjects; Group (A): 40 patients with GD and Group (B): 40 healthy control subjects recruited from endocrinology clinic at Ain Shams University Hospitals in the period between December 2020 and June 2021. All the included GD patients suffered from GO. Results: SEPP levels “as a marker of selenium status" were significantly lower in GD patients than control subjects. No significant correlation was found between selenium status and GO severity or activity. Conclusion: GD patients are markedly selenium deficient. There is lack of association between selenium status and GO severity and activity.