Options for mechanical ventricular assistance in pediatric patients are limited. Extracorporeal membrane oxygenation is used in most cases for short-term support. The TandemHeart circulatory support system is an established device that is used in adult patients to provide short-term ventricular support. In this article, we report three children in whom a TandemHeart ventricular assist device was used for right ventricular support, two after heart transplantation and another for failed Fontan physiology. Herein, we report the novel application of this technology to pediatric patients, and we discuss the lessons learned from its utilization.