Purpose: To evaluate the effects of an oral health protocol on the incidence of postoperative pneumonia in patients submitted to coronary artery bypass grafting and to valve surgery. Methods: All patients admitted to a public cardiac surgery hospital were examined by a dentist and had a thorough dentistry anamnesis and an intraoral exam focusing on teeth, gums, and tongue. Patients were taught how to brush their teeth and tongue and how to clean their jugal and palatal membranes. Chlorhexidine gluconate (CXG) 0.12 % oral rinse twice a day was used until surgery. Data on age, sex, comorbidities, oral evaluation, type of surgery, and development of pneumonia were obtained. Statistical analysis was done on these variables to evaluate the impact of the study protocol. Results: A total of 226 patients were enrolled, 136 male (60.2 %). The median age was 59 years. There were 123 (54.4 %) patients with coronary artery disease and 103 (45.6 %) with valve disease. There were 18/226 (8 %) postoperative pneumonias (PP), nine in each group. Ten occurred in dentate patients and eight in edentulous ones. Oral health optimization was achieved in 208/226 (92 %) of patients in the preoperative period. The presence of tongue plaque (OR 17, P\0.001) and of poor hygiene of the total superior dentures (OR 25, P\0.001) in the preoperative period significantly increased the chance of PP. The use of CXG 0.12 % in the preoperative period (OR 0.06, P\0.001) and on the day of surgery (OR 0.002, P\0.001) was protective against PP. Mortality in patients without pneumonia was 9/208 (4.32 %) vs. 6/19 (33.3 %) in those with pneumonia. The presence of pneumonia increased the chances of death by 11 times (P\0.001). The mean pneumonia rate in ICU in the 6 months before the study protocol was 32 per 1,000 ventilator-days, 24 during the 6-month intervention period, and 10 during the next 6 months following the study. Conclusions: PP rates were reduced using a simple and efficient protocol of dental care that improved oral hygiene in the preoperative period of cardiac surgery patients.