PURPOSE: This study evaluated the impact of preoperative oral hygiene on the incidence of postoperative pneumonia (PP) and surgical site infection (SSI) in patients undergoing esophageal cancer surgery considering the influence of COVID-19 and developing effective perioperative oral care methods. METHODS: The medical records of patients who underwent esophageal cancer surgery between January 2017 and March 2022 were analyzed. Patient characteristics and the incidence of PP and SSI before and during COVID-19 were compared. A multiple logistic regression analysis was performed with PP and SSI as the dependent variables. RESULTS: This analysis included 207 participants. The mean age was 66.6 ± 8.3 years old, and 78.3% were male. There were no significant changes in the incidence of PP or SSI before and during the COVID-19 pandemic. Preoperative xerostomia significantly increased the risk of PP (odds ratio = 3.34, 95% confidence interval 1.10-10.08, p = 0.033), an advanced cancer stage, and recurrent laryngeal nerve palsy. Surgical procedures and reconstructive organs, but not preoperative oral hygiene factors, were associated with SSI. CONCLUSIONS: The incidence of PP and SSI in patients with esophageal cancer showed no marked changes before or during the COVID-19 pandemic. Managing preoperative xerostomia may be crucial for reducing the risk of PP.