Abstract : Background: Inflammation and immune-mediated reactions are facilitated by the endothelial cell adhesion molecule intercellular adhesion molecule-1 (ICAM-1). In patients with coronavirus disease 2019 (COVID-19), viral infection of endothelial cells brought on by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can result in vascular alterations and boost the expression of ICAM-1, and may be utilized as a biomarker to assess disease severity. The purpose of this study was to determine how serum ICAM-1 levels affected the severity and prognosis of COVID-19. Materials and Methods: 120 patients with COVID-19 participated in the research. According to the severity of the condition, the COVID-19 patients were divided into three groups: critical disease (n = 23), severe disease (n = 37), and mild/moderate disease (n = 60), with 60 healthy volunteers working as the control group. Blood samples were taken as well as all of the patients' fundamental clinical and demographic information.