Background andAim: Vitamin D is a hormone with essential roles in both cellular metabolism and immunity. It controls calcium homeostasis and modulates innate and adaptive immune system responses. Many studies suggested an association between vitamin D deficiency and clinical outcomes of covid-19 infection, while others failed to document such a relation. The present study aimed to evaluate the clinical and prognostic significance of baseline vitamin D levels in hospitalized Egyptian covid-19 patients. Patients and Methods: The present retrospective study included 300 hospitalized covid-19 patients. Patients were submitted to standard clinical, laboratory, and radiological assessment. According to vitamin D levels, patients were classified to have normal levels (≥30), insufficient levels (20-29) or deficient levels (<20). Results: According to their vitamin D levels, patients were classified into those with normal vitamin D (n=135), others with vitamin D insufficiency (n=114), and a third group with vitamin D deficiency (n=51). Patients with normal vitamin D levels and vitamin D insufficiency are significantly younger [median (IQR): 49.0 (39.0-57.0) versus 51.0 (40.0-61.0) and 55.0 (43.0-62.0) years, respectively, p=0.012] and had less frequency of severe disease (24.4% versus 40.4% and 51.0%, respectively) when compared with those with vitamin D deficiency. Moreover, they had significantly lower levels of D dimer [median (IQR): 1.