Background:Coronavirus disease 2019 (COVID-19), caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been declared as a pandemic in 2019-2020. Most cases are usually self- limited; however, it may unpredictably progress to severe form with high mortality rate. Objectives: To highlight the role of measuring serum procalcitonin (PCT) and receiving early prophylactic antibiotic therapy in terms of their relation to the mortality rate in hospitalized critical COVID-19 patients. Methods: this study analyzed sixty COVID-19 critical patients admitted to Tanta University Isolation Hospital from June to November, 2020. Respiratory tract and blood samples were collected Results: Our results showed that the mean serum PCT levels were significantly higher in deceased patients (15%) than in those who could survive corona-virus infection. Patients who received early prophylactic antibiotic therapy showed significant better survival rate than those who didn't. Conclusion: This study demonstrated that measuring PCT shows statically significant results with COVID-19 patients' outcome more than other commonly used laboratory markers such as CRP. Moreover, early administration of prophylactic antibiotic therapy in COVID-19 patients, especially critical ones, is crucial even in those with negative PCT values.