The authors describe a very rare and previously unreported complication of thoracoscopic discectomy. Endoscopic spine surgery has evolved as a safe and effective treatment, and thoracoscopic discectomy, in particular, provides several advantages over open approaches, although it can be associated with intraoperative or postoperative complications. The most frequently observed adverse events are intercostal neuralgia, retained disc fragments, durotomies, atelectasis, extensive bleeding, and emergency conversion to open thoracotomy for vascular injuries. Even rare complications, such as chylorrhea or brain hemorrhagic infarction, have been reported. Nonetheless, a literature review did not reveal any case of postoperative intraabdominal hematoma following thoracoscopic discectomy. A 43-year-old woman, with no history of hematological or vascular disorders or thoracic surgery, underwent a right-sided thoracoscopic discectomy for T11–12 disc herniation. No apparent surgical technique–related complications were encountered, but intermittently repeated difficulties with single-lung ventilation occurred. The resultant dysventilation allowed partial right lung reexpansion, along with increased abdominal pressure. The latter induced an upward ballooning of the right diaphragm with consequent obstruction of the surgical field of view, requiring constant and continuous pressure applied to the thoracic surface of the diaphragm via a metal fan retractor and thus counteracting the increased abdominal pressure. Postoperatively, a large subdiaphragmatic hematoma originating from a bleeding right inferior phrenic artery was diagnosed and required urgent endovascular occlusion. The patient made an uneventful recovery with conservative treatment. A very rare and previously unreported complication—that is, early subdiaphragmatic hematoma after thoracoscopic discectomy—is described here. The authors submit that conversion to an open approach is safer when persistent anesthesia-related complications are encountered in thoracoscopic discectomy.