Background <p>Advanced esophageal squamous cell carcinoma (ESCC) may require combined resection or result in non-curative resection, increasing the risk of severe complications related to the posterior mediastinal dead space created after esophagectomy, such as airway instability and mediastinitis. Although filling this space with the greater omentum via the posterior mediastinal route is commonly used, this approach may impair gastric conduit alignment and function due to intrathoracic negative pressure. We developed a novel technique to overcome these limitations.</p> Methods <p>We retrospectively reviewed 20 patients who underwent esophagectomy with gastric conduit reconstruction and additional omental transposition using a novel “waterfall” method between 2012 and 2022. Omental transposition was selectively added in cases involving combined resection of adjacent organs or non-curative resection, in which the posterior mediastinal dead space was considered to increase postoperative complication risk. In this technique, the greater omentum is elevated to the neck with the gastric conduit via the retrosternal route and then pulled down from the anterior mediastinum to fill the posterior mediastinal dead space. Surgical outcomes, postoperative complications, and conduit-related symptoms were evaluated.</p> Results <p>Sixteen patients had cT4b disease and four had cT3 disease. Curative resection was achieved in 12 patients, while 8 underwent non-curative resection. No serious complications such as airway necrosis, airway–mediastinal fistula, or mediastinitis were observed, and no patients developed gastric conduit dysfunction.</p> Conclusions <p>The waterfall method is a safe and feasible technique for filling the posterior mediastinal dead space after esophagectomy while preserving gastric conduit alignment and function in high-risk ESCC cases.</p>