Diabetic ketoacidosis (DKA) occurs frequently among children and adolescents with type 1 diabetes. Although a number of complications may occur during episodes of DKA, significant cardiac arrhythmias are uncommon. We present the case of an adolescent who presented with severe DKA and wide complex tachycardia that was unresponsive to multiple doses of adenosine and ultimately required synchronized cardioversion. This case reminds the clinician of the importance of cardiac monitoring in children with DKA, particularly in the setting of hyperkalemia.