We examined the use of intraoperative thermal imaging to assess the gastric vascularization and gastric tube viability during esophagectomy. The surface temperatures of the intact stomach, devascularized stomach, and gastric tube were measured in 13 patients from the proximal end to the pylorus longitudinally along the greater curvature or along the entire gastric tube during esophagectomy. Thermal images clearly demonstrated a surface temperature decline in the proximal region of the gastric tube. The mean decline rate in the surface temperature in the proximal region of the gastric tube in comparison to the intact stomach was 17.7% (P < 0.001). One patient who developed gastric tube necrosis exhibited a prominent drop in the surface temperature in the proximal region of 20.6% in comparison to that in the distal region, compared to that of 12.5% in other patients. Intraoperative thermal imaging is a noninvasive and reliable technique for the assessment of the gastric tube viability.