Noninvasive ventilation (NIV) has emerged as a powerful tool for the pediatric emergency management of acute respiratory failure (ARF). This therapy is safe and well tolerated and seems to frequently prevent both the need for invasive mechanical ventilation and the associated risks/complications. Although NIV can be the primary treatment of ARF resulting from multiple respiratory disease states, it must be meticulously monitored and, when unsuccessful, may aid in preoxygenation for prompt endotracheal intubation and invasive mechanical ventilation. The following article reviews the physiologic effects of NIV and its role in common respiratory diseases encountered in pediatric emergency medicine.