The pandemic of COVID-19, a disease caused by a novel coronavirus (CoV), SARS-CoV-2, is causing substantial morbidity and mortality. Older age and presence of diabetes mellitus, hypertension, and obesity significantly increases the risk for hospitalization and death in COVID-19 patients. In this Perspective, informed by the studies on severe acute respiratory syndrome, SARS-CoV, and Middle East respiratory syndrome, MERS-CoV, and the current literature on SARS-CoV-2, we discuss potential mechanisms by which diabetes modulates the host-viral interactions and host-immune responses. We hope to highlight gaps in knowledge that require further studies pertinent to COVID-19 in patients with diabetes.