The incidence of anastomotic leakage after esophagectomy remains around 10%. It was previously reported that PDSII rapidly loses tensile strength at pH 1.0 and pH 8.5. By contrast, LACLON degradation is reportedly insensitive to pH. We therefore compared LACLON with PDSII for esophago-gastric conduit, layer-to-layer, handsewn anastomosis. Between January 2016 and January 2020, 90 patients who received posterior mediastinal gastric conduit reconstruction with layer-to-layer handsewn anastomosis (51 using PDSII and 39 using LACLON) at Akita University Hospital were enrolled. The incidence of anastomotic leakage was significantly lower in the LACLON (2.6%, 1/39 patients) than PDSII group (15.7%, 8/51 patients) (p = 0.0268). Multivariable logistic analysis showed the risk of anastomotic leakage was significantly greater with PDSII than LACLON (odds ratio 11.01; 95% CI 1.326-277.64; p = 0.024). The percentages of time the pH was higher than 8 on the gastric conduit side of the anastomosis were 3.1%, 5.7%, 20.9% and 80.5%, respectively, in the four most recent patients. The present study showed that pH at the anastomosis soon after esophagectomy tends to be alkaline rather than acidic, which raises the possibility that this alkalinity facilitates the deterioration of surgical sutures including PDSII.