Background: Zenker’s diverticulum arises from the posterior hypopharyngeal wall through Killian’s dehiscence and predominantly affects older adults. Surgical and endoscopic treatments may be complicated by adverse events, including recurrent laryngeal nerve injury, cervical emphysema, mediastinitis, and pharyngoesophageal fistula formation. Methods: We report the case of a 69-year-old male who underwent open surgical treatment for Zenker’s diverticulum and subsequently developed an upper esophageal fistula complicated by a retroesophageal abscess. Results: The patient was treated using an externally adapted endoluminal vacuum-assisted closure system (EndoVAC), which enabled continuous drainage, local lavage, and progressive closure of the esophageal defect. Conclusions: Endo-VAC therapy represents a safe and minimally invasive therapeutic option for the management of postoperative esophageal fistulas following Zenker’s diverticulum surgery and may reduce the need for extensive esophageal reconstruction.