Adenosine by rapid intravenous bolus is frequently utilized in clinical practice as both a pharmacologic treatment for supraventricular (reentrant) tachycardia and in provocative testing for the diagnosis of Wolff-Parkinson-White (WPW) syndrome. This is a case report of an otherwise healthy adolescent female who received adenosine during a provocative test for WPW syndrome. Immediately after receiving adenosine, the patient had a self-limited episode of atrial fibrillation. When administering adenosine, teams should be aware of the potential adverse effects and be prepared to treat appropriately.