The novel coronavirus disease 2019 COVID-19 pandemic reached over 528 million confirmed infections and claimed the lives of more than 6 million people worldwide. The clinical features of COVID-19 are diverse and range from asymptomatic to critical illness and death. Severe and critical cases represented 14% and 5% of laboratory-confirmed COVID-19 patients, respectively. Severe patients present signs of dyspnea, respiratory frequency ≥ 30/min, blood oxygen saturation ≤ 93%, partial pressure of arterial oxygen to fraction of inspired oxygen ratio < 300 mmHg, and/or lung infiltrates > 50% within 24 to 48 hours. Critically ill cases may experience respiratory failure that requires mechanical ventilation, shock, disseminated coagulopathy, and other organs failure requiring admission to the intensive care unit (ICU). A good understanding of the possible risk factors in combination to disease immunopathology associated with COVID-19 severity is helpful for clinicians in identifying patients who are at high risk and require prioritized treatment to prevent disease progression and adverse outcome. Risk factors range from demographic factors, such as age, sex and ethnicity, diet and lifestyle habits to underlying diseases and complications, and laboratory indications. Many studies have reported predictive models using various risk factors to identify high-risk patients that may develop severe and critical illness. It is worth noting that some studies address the risk factors of COVID-19 development in general, without any focus on disease severity, while others specifically focus on risk factors for disease progression to a critical stage.