Corticosteroid therapy has become an important modality of treatment for diseases in which rapid control of immunoinflammatory processes is required. However, one of the serious, but less known adverse effect of this therapy is cardiac arrhythmias. This includes both tachyarrhythmias and bradyarrhythmias. Corticosteroid use may also be associated with electrolyte imbalances like hypokalaemia by its mineralocorticoid activity. Those side effects are mainly seen with high-dose intravenous methyl-prednisolone or oral pulse dose prednisolone therapy. Here we report our experience in a child with warm idiopathic autoimmune haemolytic anaemia who developed sinus bradyarrhythmias and treatment refractory hypokalaemia during low-dose steroid therapy with reduction in heart rate by 60% of baseline.