The presence of pathogens in dental plaque is a risk factor associated with postoperative pneumonia in esophageal cancer patients. The effectiveness of pre-operative dental brushing to decrease the risk of postoperative pneumonia in esophageal cancer patients was evaluated prospectively.A total of 86 thoracic esophageal cancer patients who underwent an esophagectomy were investigated. Patients were divided into 2 groups: the control group (41 patients) and the pre-operative dental brushing group (45 patients). The patients in the brushing group were assigned to brush their teeth 5 times a day. After the operation, the frequency of postoperative pneumonia and need for tracheostomy for pulmonary treatment was calculated.Postoperative pneumonia was decreased markedly from 32% to 9% (P = .013), and the frequency of postoperative pneumonia requiring tracheostomy decreased from 12% to 0% in the dental brushing group, respectively. Limiting the patients who had positive pathogenic bacteria in their dental plaque on their admission, the frequency of postoperative pneumonia was decreased from 71% (5 of 7 patients) in the control group to 17% (2 of 12 patients) in the dental brushing group (P = .045).Frequent pre-operative dental brushing is performed easily and seems to prevent postoperative pneumonia in esophageal cancer patients.