Abstract Background: SARS can cause multiple organ injury where the major organ affected is the lung. It has a deleterious effect on the thyroid gland. The viral infection and the thyroid gland-have a complex interplay through immunomodulatory signal-ing molecules and hormones. Aim of Study: Was to evaluate the prevalence of thyroid dysfunction in patients infected with COVID-19 virus, com-pare thyroid function tests and thyroid antibodies in patients with COVID-19 disease admitted in ward and patients with COVID-19 disease admitted in ICU and its correlation with the demographic variables, comorbidities, and some laboratory tests. Material and Methods: This cross-sectional study was conducted, including 200 patients diagnosed with COVID-19 virus disease admitted in both ward and ICU at Kasr Al-Airy Internal Medicine Isolation Hospital in Cairo, Egypt, from June 2021 to May 2022. Thyroid function tests, thyroid anti-bodies were done. Demographic, clinical, and laboratory data were analyzed. Results: Sick euthyroid syndrome was the most common thyroid dysfunction among our patients. Serum levels of TSH and free T4 levels were significantly lower in ICU patients compared to ward patients (p-value: 0.044 and <0.001, respec-tively), while serum levels of total T3 and total T4 levels were significantly higher in ICU patients compared to ward patients (p-value s0.001 for both). Female gender, diabetes, serum lev-el of total T4, and anti thyroglobin antibodies were associated with higher risk of ICU admission among COVID-19 patients. Total T3 was the most sensitive marker for ICU admission with 933% sensitivity while free T4 was the most specific mark-er for ICU admission with 70.3% specificity among the study group. Conclusion: Thyroid dysfunction is prevalent in COV-ID-19 patients, with sick euthyroid syndrome being the most common thyroid dysfunction. There were significant differenc-es in the serum levels of TSH, free T4 and total T3 and T4 be-tween COVID-19 patients admitted in ward and those admitted in ICU. Total T3 was the most sensitive indicator while T4 was the most specific indicator for ICU admission. Early detection and treatment of thyroid abnormalities in patients with COV-ID-19 is crucial.