Establishing the etiology of tachycardia in a trauma patient is often difficult. Pediatric trauma patients present an even tougher challenge. Cardiac contusion should be suspected when other more common traumatic injuries that produce hypoxia and blood loss are excluded. The diagnosis of cardiac contusion is notoriously difficult to make largely due to the controversy over the definition of the disease, and the lack of a true gold standard confirmatory test. Atrioventricular nodal reentrant tachycardia (AVNRT) is a common form of supraventricular tachycardia (SVT) that can also present a diagnostic challenge to emergency physicians. While electrophysiologic studies are the gold standard for confirming the diagnosis, there are certain aspects of the history, electrocardiogram (ECG), and responses to cardiac maneuvers that strongly suggest the diagnosis. We present the case of a pediatric trauma patient that presented with new onset AVNRT masquerading as cardiac contusion.