More than 8,000 individuals with COVID-19 have been admitted to the Mount Sinai Health System. As Mount Sinai’s front-line doctors, nurses, and staff treated patients with the disease, they were able to improve outcomes by working closely with their colleagues in other specialties and in laboratories at the Icahn School of Medicine at Mount Sinai. In this article, researchers and physicians discuss what they have learned about COVID-19, including the identification of complicating factors, the biology of the disease, and the broad range of organ damage inflicted by it. The Mount Sinai team also discusses their innovative convalescent plasma therapy and the benefits of anticoagulant treatment.