Cardiac arrhythmias often present as urgent medical conditions requiring immediate care. Patient presenting with a tachyarrhythmia is a common finding in the emergency room. They also occur commonly in patients undergoing non-cardiovascular procedures including surgeries. It is thus pertinent that the physician handling such cases must be appropriately trained to diagnose and provide emergency management till the case is referred to a specialist. Most cases present as narrow or a wide complex tachycardia. The differential diagnosis is arrived at by deciding on the ECG morphology alongwith relevant history and physical examination where feasible. This article describes the bedside approach to diagnose and treat an arrhythmia presenting as a narrow complex.