Purpose: Anastomotic leakage after resection of gastroesophageal junction cancer is a dangerous complication, and leakage rates have remained stable for decades. Perfusion is crucial for anastomotic healing, but traditional perfusion assessment is limited in a minimally invasive environment. New methods as indocyanine green fluorescence angiography (ICG-FA) have proven promising, but quantitative analysis has been challenging. This study aimed to demonstrate the feasibility and usability of real-time intraoperative quantitative fluorescence angiography (q-ICG) with a touchscreen tablet. Methods: A software for q-ICG was previously developed and validated. Ten patients underwent perfusion assessment in white light (WL), with ICG-FA, and with q-ICG during Ivor-Lewis esophageal resection. The usability of the tablet-based software was tested with the System Usability Scale (SUS®). Furthermore, we investigated the differences in perfusion assessment as the distance from the conduit margin to a surgeon selected point of sufficient perfusion for anastomosis using the different modalities. Results: Q-ICG was successful in all patients, with an excellent median SUS® of 82.5 (77.5–93.8). Significant differences in distances from the conduit margin to points of sufficient perfusion selected by the surgeons were found: ICG: WL = 14.1 mm (p = 0.048), q-ICG: WL = 32.08 mm (p < 0.001), and q-ICG: ICG = 17.95 mm (p = 0.002). Furthermore, significant differences of perfusion were found between the points, when q-ICG was performed retrospectively in the surgeon selected areas (p = 0.008–0.013). Conclusion: Real-time intraoperative touchscreen-based q-ICG was feasible with excellent usability, and differences in sufficient perfusion points selected by the surgeons between modalities were found. Further studies should focus on clinical relevance and determine cutoff values associated with anastomotic leakage.