Patients with diabetes have increased susceptibility to infection with Severe acute respiratory syndrome-coronavirus 2 and increased morbidity and mortality from Coronavirus disease 2019 (COVID-19) infection. Mortality from COVID-19 is sometimes caused by cardiac arrhythmias. Electrolyte disturbances in patients with diabetic ketoacidosis (DKA) can increase the risk of cardiac arrhythmias. Despite these correlations, little has been reported about the co-incidence of these three conditions: COVID-19, DKA and cardiac arrhythmias. In this case report we describe two children with COVID-19, new-onset DKA and cardiac arrhythmias. These cases emphasize the importance of close cardiac and electrolyte monitoring in patients with COVID-19 infection.