Coronavirus disease (COVID-19) is a new viral illness that affects not only the respiratory system but also leads to multiorgan involvement. Till now, no curative treatment is available; prevention is the only way to reduce the number of infected cases. Low serum level of vitamin D has been implicated in increased susceptibility to coronavirus infection and disease severity. However, there is no conclusive evidence as regards the role of vitamin D in COVID-19 infection and outcome. This study aimed to evaluate the serum level of Vit D in patients with COVID-19 and highlights its prognostic significance. A total of 109 COVID-19 patients' medical records were selected and retrospectively analyzed from Ohoud Hospital in Medina. Data collection was done in the period between 1/4/2020 and 22/2/2021 followed by statistical analysis. The median age for COVID-19 patients was 54 years old. The level of Vit-D was low in patients with COVID-19 with a median of 15.2 ng/ml. Serum ferritin was high in all COVID-19 patients with a median of 720.9 ng/ml. There was a significantly higher rate of developing severe forms of COVID-19 in males compared to females, P-value < 0.001. Serum vitamin D level was significantly lower in patients with COVID-19 compared to control with P-value < 0.001. More reduction in Vit-D level was detected in the severe form of COVID-19 (P-value 0.042). There were significantly lower levels of vitamin D and higher levels of ferritin in the server covid-19 cases, P-values of 0.018 and 0.001, respectively. Low serum Vitamin-D level was significantly associated with a higher risk of COVID-19 infection and a more severe form of the disease that may end by death. Vitamin D supplementation will provide a sufficient serum level of the vitamin that can prevent infection and or minimize COVID-19 severity. Keywords: COVID-19, vitamin D deficiency.