Zenker's diverticulum (ZD) is an outpouching of tissue through the Killian triangle that is believed to be caused by dysfunction of the cricopharyngeal muscle. ZD is a relatively uncommon disorder occurring in the elderly. The predominant symptom of ZD is dysphagia, and the most serious consequence is pulmonary aspiration. Videofluoroscopy confirms the diagnosis. Therapy of symptomatic ZD has evolved from an open surgical approach to less invasive transoral endoscopic techniques. Transoral endoscopic therapy using rigid instruments is performed primarily by otorhinolaryngologists, whereas transoral therapy using flexible endoscopes is performed by surgical endoscopists and gastroenterologists. The common goal of all modalities is severing of the septum between the esophageal lumen and the diverticulum containing the cricopharyngeal muscle. Although flexible endoscopic therapy was described nearly 20 years ago, it has experienced a recent resurgence paralleling the advancements of therapeutic endoscopy in other areas, such as endoscopic submucosal dissection. Direct head-to-head comparisons of rigid and flexible endoscopic therapy are lacking, and each approach has variations in techniques as well as advantages and disadvantages. In this article, we review the pathophysiology and management of patients with ZD with an emphasis on flexible endoscopic therapy.