In patients with severe coronavirus disease 2019 (COVID-19) with diabetes, glycemic control is essential for a better outcome, however, we face difficulty controlling hyperglycemia induced by high-dose glucocorticoids. We report five cases of severe COVID-19 patients with diabetes, whose glycemic control was managed using an intermittently scanned continuous glucose monitoring (isCGM) system during methylprednisolone therapy. Patients using isCGM showed significantly lower average blood glucose levels and significantly higher total daily insulin dose during the methylprednisolone therapy, compared to patients under regular blood glucose monitoring. The use of isCGM enables remote glucose monitoring, and this can reduce the risks of healthcare workers who have frequent contact with the patients. Thus, we suggest that using isCGM should be considered in hospitalized patients with diabetes under the COVID-19 pandemic to achieve better glycemic control and to minimize the possible risks of healthcare workers.