Coronaviruses are single-stranded ribonucleic acid viruses that can cause illnesses in humans ranging from the common cold to severe respiratory disease and even death.In March 2020, the World Health Organization declared the 2019 novel coronavirus disease (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as the first pandemic. Compared to women, most countries with available data report that men with COVID-19 have greater disease severity and higher mortality. Lab and animal data indicate that men respond differently to the SARS-CoV-2 infection, offering possible explanations for the epidemiologic observations. The plausible theories underlying these observations include sex-related differences in angiotensin-converting enzyme 2 receptors, immune function, hormones, habits, and coinfection rates.In this review we examine these factors and explore the rationale as to how each may impact COVID-19. Understanding why men are more likely to experience severe disease can help in developing effective treatments, public health policies, and targeted strategies such as early recognition and aggressive testing in subgroups.